The string is a set of characters. In PHP, the symbol is the same as the byte, it means that it is possible exactly 256 different characters. It also means that PHP has no built-in support for Unicode "a. Some Unicode support" A provides the UTF8_ENCODE () and UTF8_DECODE () functions.

Note: There are no problems if the string is very high. There are practically no restrictions on the size of the lines imposed by PHP, so there is absolutely no reason to worry about their length.

Syntax

The string can be determined in three different ways.

Single quotes

The simplest way to determine the string is to conclude it into single quotes (symbol ").

To use a single quotes inside the line, as in many other languages, it must be predicted by a symbol of the inverse scythe (\\), that is, shielding it. If the reverse sinking damn should go before a single quotion or be at the end of the line, you need to duplicate it. Please note that if you try to shield any other character, the reverse sink feature will also be printed! So, as a rule, there is no need to shield the reverse oblique line.

Note: In PHP 3, in this case, the E_NOTICE level message will be issued.

Note: Unlike two other syntaxes, variables and shielding sequences for special characters encountered in lines enclosed in single quotes are not processed.

Echo "This is a simple string"; ECHO "You can also insert a symbol of a new line in such a way as it is normal"; // Will out: once Arnold said: "I" LL Be Back "Echo" once Arnold said: "I \\" LL BE Back ""; // Remove: You removed C: \\ *. *? Echo "You removed C: \\\\ *. *?"; // Remove: You removed C: \\ *. *? Echo "You removed C: \\ *. *?"; // Will out: it will not insert: \\ N new line Echo "It will not insert: \\ N new string"; // Will out: $ EXPAND variables also $ either are not substituted with ECHO "$ Expand variables also $ either are not substituted";

Double quotes

If the string is enclosed in double quotes ("), PHP recognizes a greater number of control sequences for special characters:

Table 11-1. Control sequences

We repeat if you want to multiply any other character, the reverse sink feature will also be printed!

But the most important property of rows in double quotes is the processing of variables. See more detail: Row processing.

Heredoc.

Another way to define strings is the use of HEREDOC-syntax ("

The closing identifier must begin in the first column of the string. In addition, the identifier must correspond to the same rules of naming as all other tags in PHP: contain only alphanumeric characters and an underscore sign, and should begin with non-merpure or underscore.

Attention

It is very important to note that the string with the closing identifier does not contain other characters, except, possibly semicolons (;). This means that the identifier should not be entered with an indent and that there can be no gaps or tabs of the tab before or after a semicolon. It is also important to understand that the first character in front of the closing identifier should be a symbol of a new string defined in your operating system. For example, on Macintosh it \\ r.

If this rule is broken and the closing identifier is not "pure", it is believed that the closing identifier is missing and PHP will continue to search on. If in this case the correct closing identifier will not be found, it will cause an error in processing with a string number at the end of the script.

Heredoc-text behaves the same way as a row in double quotes, while not having them. This means that you do not need to shield quotes in HEREDOC, but you can still use the above control sequences. Variables are processed, but using complex variables inside Heredoc should also be attentive as when working with lines.

Example 11-2. An example of the definition of a HEREDOC string

$ STR \u003d.<<foo \u003d "foo"; $ this-\u003e bar \u003d array ("Bar1", "Bar2", "Bar3"); )) $ foo \u003d new foo (); $ name \u003d "mine"; Echo.<<foo. Now I bring ($ Foo-\u003e Bar). This should output the title letter "A": \\ x41 EOT;

Note: Heredoc support has been added to PHP 4.

Processing of variables

If the string is defined in double quotes, or with HEREDOC, the variables inside it are processed.

There are two types of syntax: simple and complex. Simple syntax is easier and convenient. It allows the variable processing, the value of the array (array) or object properties (Object).

Complex syntax was introduced into PHP 4 and can be recognized on curly brackets surrounding the expression.

Simple syntax

If the interpreter meets the dollar sign ($), it captures so many characters as possible to form the correct variable name. If you want to accurately define the end of the name, conclude a variable name in curly brackets.

$ beer \u003d "heineken"; Echo "$ Beer" S Taste Is Great "; // works," "" This is an incorrect character for the name of the ECHO "He Drank Some $ Beers" variable; // does not work, "s" is a faithful character for the echo variable name "He Drank Some $ (Beer) S"; // ECHO "HE DRANK SOME ($ Beer) s"; // works

An array element (array) or object property (Object) can also be processed. In the array indexes, the closing square bracket (]) denotes the end of the definition of the index. For the properties of the object, the same rules apply as for simple variables, although it is impossible to the trick, as with variables.

// These examples are specifically about the use of arrays inside // Lines. Outside the rows Always enter your string keys // Array in quotes and do not use outside strings (brackets). // Let's show all errors Error_Reporting (E_ALL); $ Fruits \u003d Array ("Strawberry" \u003d\u003e "Red", "Banana" \u003d\u003e "Yellow"); // Works, but notice that outside the quotes of the line works in another ECHO "A BANANA IS $ FRUITS."; // ECHO "A BANANA IS ($ FRUITS [" BANANA "])."; // Works, but PHP, as described below, first searches // Constant Banana. ECHO "A BANANA IS ($ Fruits)."; // Does not work, use curly brackets. This will cause a processing error. ECHO "A BANANA IS $ FRUITS [" BANANA "]."; // ECHO "A BANANA IS" works. $ Fruits ["Banana"]. "."; // running Echo "This Square is $ Square-\u003e Width Meters Broad."; // Does not work. For solution, see complex syntax. Echo "This Square is $ Square-\u003e Width00 Centimeters Broad.";

For something more difficult, you must use complex syntax.

Complex (figured) syntax

It is called difficult because it is difficult in understanding, but because it allows you to use complex expressions.

In fact, you can enable any value in the name of the name in the string with this syntax. You just write down the expression in the same way as outside the line, and then conclude it in (and). Since you cannot shield "(", this syntax will be recognized only when $ should be directly for (. (Use "(\\ $" or "($" to display "($"). Several explanatory examples:

// Let's show all errors Error_Reporting (E_ALL); $ Great \u003d "Fantastic"; // does not work, removes: this is (Fantastic) Echo "This is ($ Great)"; // Works, withdraw: This is Fantastic Echo "This is ($ Great)"; Echo "This is $ (Great)"; // runs Echo "This width square ($ Square-\u003e Width) 00 centimeters."; // running echo "it works: ($ arr)"; // It is incorrect for the same reason as $ Foo is incorrectly out // Row. In other words, it will still work, // But since PHP is first looking for a foo constant, it will call it // E_NOTICE level error (indefinite constant). Echo "It is wrong: ($ ARR)"; // Works. When using multidimensional arrays, inside // Lines Always use the ECHO curly brackets "it works: ($ arR [" FOO "])"; // Works. Echo "It works:". $ arr ["foo"]; Echo "You can even write ($ OBJ-\u003e VALUES-\u003e NAME)"; Echo "This is the value of a variable named $ Name: ($ ($ Name))";

Access to the symbol in the string and its change

Symbols in lines can be used and modified by defining their offset relative to the start of the string, starting from zero, in curly brackets after the row.

Note: To ensure backward compatibility, you still have the ability to use the array bracket for the same objectives. However, starting with PHP 4, this syntax is undesirable to use.

Example 11-3. Several examples of string

// Obtaining the first line character $ str \u003d "This is a test."; $ first \u003d $ str (0); // Obtaining the third character line $ third \u003d $ STR (2); // Obtaining the last character of the line $ str \u003d "It's still a test."; $ Last \u003d $ STR (STRLEN ($ STR) -1); // Changing the last symbol of the line $ str \u003d "Look at the sea"; $ STR (STRLEN ($ STR) -1) \u003d "I";

Useful features and operators

Rows can be combined with the operator. "." (point). Please note the addition operator "+" does not work here. For more information, see String Operators.

For modifying strings, there are many useful features.

The main functions are described in the section of string functions, the functions of regular expressions for advanced search and replacement (in two parts: perl and POSIX advanced).

There are also functions for URL strings, and functions for encryption / decryption strings (MCRYPT and MHASH).

Finally, if you still did not find what you were looking for, see also functions for symbolic type.

Convert to string

You can convert a value to a string using the string (String) or the STRVAL () function. In expressions where the string is necessary, the conversion occurs automatically. This happens when you use the ECHO () or print () functions, or when you compare the value of a variable with a string. Reading the sections of the Types and manipulation of types will make the following more understandable. See also setType ().

Boolean (Boolean) The value of True is converted into the string "1", and the value of False is represented as "" (empty string). By this way, you can convert values \u200b\u200bin both directions - from Boolean type into a string and vice versa.

An integer (integer) or a floating point number (Float) is converted to a string represented by the number consisting of its numbers (including an indicator of the degree for a floating point numbers).

Arrays are always converted to the "Array" string, so that you cannot display the contents of the array (Array) using ECHO () or PRINT () to find out what it contains. To view one element, you need to do something like an echo $ arr ["foo"]. See below Tips on how to display / view all content.

Objects are always converted to the "Object" string. If you want to display the value of the object member of the object (Object) in order to debug, read the following paragraphs. If you want to get the name of the class of the desired object, use get_class ().

Resources are always converted into strings with the "Resource ID # 1" structure, where 1 is a unique resource number (Resource) assigned to it in PHP during execution. If you want to get a resource type, use.

NULL is always transformed into an empty string.

As you could see above, the output of arrays, objects or resources does not provide you with any useful information about the values \u200b\u200bthemselves. A more appropriate way to display values \u200b\u200bfor debugging is to use the Print_R () and var_dump () functions.

You can also convert PHP values \u200b\u200binto strings for constant storage. This method is called serialization and can be performed using the Serialize () function. In addition, if you have a WDDX support in your PHP setting, you can serialize PHP values \u200b\u200bin the XML structure.

Row conversion in numbers

If the string is recognized as a numeric value, the resulting value and the type is defined as shown below.

The string will be recognized as Float if it contains any of the characters. "," E ", or" E ". Otherwise, it will be defined as a whole.

The value is determined by the initial part of the line. If the string begins with a correct numeric value, this value will be used. Otherwise, the value will be 0 (zero). A faerful numeric value is one or more digits (which can contain a decimal point), at the request of the sign presented, followed by an optional indicator. The degree indicator is "E" or "E" with subsequent one or more numbers.

$ Foo \u003d 1 + "10.5"; // $ foo is Float (11.5) $ Foo \u003d 1 + "-1.3e3"; // $ foo is Float (-1299) $ Foo \u003d 1 + "Bob-1.3E3"; // $ foo is an integer (1) $ Foo \u003d 1 + "Bob3"; // $ foo is an integer (1) $ Foo \u003d 1 + "10 Small Pigs"; // $ foo is integer (11) $ Foo \u003d 4 + "10.2 Little Piggies"; // $ foo is Float (14.2) $ Foo \u003d "10.0 PIGS" + 1; // $ foo is Float (11) $ Foo \u003d "10.0 PIGS" + 1.0; // $ foo is Float (11)

For more information on this conversion, see the UNIX StrTod (3) documentation section.

If you want to test any of the examples of this partition, you can copy and paste it and the next line to see what happens:

Echo "\\ $ Foo \u003d\u003d $ Foo; Type:". GetType ($ foo). "
\\ n ";

Do not expect to receive a symbol code by converting it to an integer (as you could do, for example, in C). To convert the characters to their codes and back, use the ORD () and

I am not an expert in programming on PHP, but I confuse me a little, why I see some code in PHP with a string concluded in single, and sometimes in double quotes.

I just know that V.Net or C language, if it is in single quotes, it means that this is a symbol, not a string.

Decision

What you need to know

$ a \u003d "name"; $ B \u003d "MY $ A"; \u003d\u003d "My Name" $ \u200b\u200bC \u003d "My $ A"; ! \u003d "MY NAME"

In PHP, people use single quotes to determine a constant string, for example "a", "My name", "ABC XYZ" when using double quotes to determine a string containing an identifier, such as "A $ B $ C $ D",

And another thing,

Echo "My Name";

faster than

Echo "My Name";

Echo "My". $ a;

slower than

Echo "MY $ A";

This is true for other rows used.

In PHP, the text in single quotes is considered as a string value, and the text in dual quotes will analyze the variables by replacing and processing their value.

$ test \u003d "variable"; Echo "Hello Mr $ Test"; // The Output Would be: Hello Mr Variable Echo "Hello Mr $ Test"; // The Output Would be: Hello Mr $ Test

Here, double quotation is analyzing the value, and single quotation is considered as a string value (without parsing a $ test variable.)

Both types of nested characters are rows. One type of quotes is convenient to use for the conclusion of another type of quotation. "" "And also" "", the greatest difference between the types of quotes is that references to nested identifiers are replaced inside the double quotes, and not inside single quotes.

Comment: In PHP 7.0.0 on 64-bit platforms there are no achievable limit restrictions for string lengths, in 32-bit systems and in earlier PHP versions, lines can not be more than 2 GB (2147483647 bytes).

Syntax

The string can be determined by four different ways:

• Single quotes
• Double quotes
• NOWDOC syntax (starting with PHP 5.3.0)

Single quotes

The simplest way to identify a string is to conclude it into single quotes (symbol " ).

To use single quotes inside the string, score it with a reverse layer ( \ ). If you need to write a reverse lay, duplicate it ( \\ ). All other cases of the application of the reverse layer will be interpreted as conventional symbols: This means that if you try to use other control sequences, such as \\ R. or \\ N.They will be derived as it is instead of any special behavior.

echo. "This is a simple string";

echo. "You can also insert into strings
symbol of the new line like this
this is normal";

// Displays: Once Arnold said: "I" LL BE Back "
echo. "Once upon a time Arnold said:" I \\ "LL BE Back" ";

Echo. "You removed C: \\\\ *. *?";

// Displays: You removed C: \\ *. *?
echo "You removed C: \\ *. *?" ;

// displays: it will not be deployed: \\ N new line
echo. "It will not be deployed: \\ N new string";

// Displays: Variables $ Expand also $ either do not unfold
echo. "$ Expand variables also $ either do not unfold";
?>

Double quotes

If the string is enclosed in double quotes ("), PHP recognizes the following control sequences of special characters:

Control sequences

Sequence	Value
\\ N.	new line (LF or 0x0A (10) in ASCII)
\\ R.	return carriage (CR or 0X0D (13) in ASCII)
\\ T.	horizontal tab (HT or 0x09 (9) in ASCII)
\\ V.	vertical tab (VT or 0x0B (11) in ASCII) (with PHP 5.2.5)
\\ E.	escape sign (ESC or 0x1B (27) in ASCII) (with PHP 5.4.4)
\\ F.	page feed (FF or 0x0C (12) in ASCII) (with PHP 5.2.5)
\\	reverse oblique damn
\$	dollar sign
\"	double Quotes
\{1,3}	The sequence of symbols corresponding to the regular expression of the symbol in the octal number system that silently overflows to fit into bytes (i.e. "\\ 400" \u003d\u003d\u003d "\\ 000")
\\ x (1,2)	The sequence of characters corresponding to the regular expression of the symbol in a hexadecimal number system
\\ U (+)	The sequence of characters corresponding to the regular expression of the Unicode symbol, which is displayed in the string in the UTF-8 view (added to PHP 7.0.0)

As in a string concluded in single quotes, the screening of any character will also display the screening symbol itself. Up to PHP 5.1.1, reverse lay \\ ($ var) Not printed.

Heredoc.

The third way to define strings is the use of HEREDOC-syntax: <<< . After this operator, you must specify the identifier, then the row translation. After that, the string itself goes, and then the same identifier that closes the insert.

Line should Begin with a closing identifier, i.e. He must stand in the first line column. In addition, the identifier must comply with the same rules of naming as all other tags in PHP: contain only alphanumeric characters and an underscore sign, and should not begin with the numbers (the underscore is permitted).

Attention

It is very important to note that the row with the closing identifier should not contain other characters, except for a semicolon ( ; ). This means that the identifier should not be introduced with indent And that there can be no gaps or tabs of tabs before or after a point with a comma. It is also important to understand that the first character in front of the closing identifier should be a symbol of a new string defined in your operating system. For example, in UNIX systems, including MacOS, this \\ N.. After the closing identifier, a new line should also begin immediately.

If this rule is broken and the closing identifier is not "pure", it is believed that the closing identifier is missing and PHP will continue to search on. If in this case the correct closing identifier will not be found, it will cause a parsing error with a string number at the end of the script.

Example # 1 Example of incorrect syntax

class foo (
Public $ Bar \u003d<<bar
EOT;
// Pencing before the closing identifier is unacceptable
}
?>

Example # 2 Example of the correct syntax

class foo (
Public $ Bar \u003d<<bar
EOT;
}
?>

Heredoc cannot be used to initialize class fields. Starting with PHP 5.3, this restriction applies only to Heredoc containing variables within itself.

Heredoc-text behaves the same way as a row in double quotes, while not having them. This means that you do not need to shield quotes in HEREDOC, but you can still use the above control sequences. Variables are processed, but using complex variables inside Heredoc should also be attentive as when working with lines.

Example # 3 Example of definition hereOC-row

$ STR \u003d.<<Sample string,
covering several lines
using HEREDOC syntax.
Eod;

Class Foo.
{
VAR $ foo;
Var $ Bar;

FUNCTION __CONSTRUCT ()
{
$ this -\u003e foo \u003d "foo";
$ this -\u003e
}
}

$ foo \u003d new foo ();
$ name \u003d "name";

echo.<<My name is "$ Name". I type $ foo -\u003e foo .
Now I take out($ Foo -\u003e Bar [1]) .
This should remove the title letter "A": \\ x41
EOT;
?>

My name is "name". I print foo. Now, I displaced BAR2. This should remove the title letter "A": a

It is also possible to use HEREDOC syntax for data transmission through the function arguments:

Starting from version 5.3.0, it became possible to incorporate static variables and properties / constants of the class using the Heredoc syntax:

Example # 5 Using Heredoc for static variable incidence

// Static variables
fUNCTION FOO ()
{
Static $ Bar \u003d<<There's nothing here...
Label;
}

// Constants / Class Properties
class Foo.
{
const Bar \u003d.<<An example of using constant
Foobar;

Public $ BAZ \u003d<<An example of using the field
Foobar;
}
?>

Starting with PHP 5.3.0, you can also surround the Heredoc identifier with double quotes:

Nowdoc.

Nowdoc is the same for strings in single quotes, as wellDoc for lines in double quotes. Nowdoc looks like heredoc, but inside it no substitution is carried out. This design is ideal for the introduction of a PHP code or other large text blocks without the need for its shielding. In this, he is a little bit like SGML design The fact that declares the text block that is not intended for processing.

Nowdoc indicates the same sequence <<< that is used in HEREDOC, but the identifier subsequent following it is single quotes, for example, <<<"EOT" . All conditions operating for Heredoc identifiers are also valid for nowdoc, especially those belong to the closing identifier.

Example # 7 An example of using Nowdoc

echo.<<<"EOD"
Example of text
occupying several lines
using the NOWDOC syntax. Inverse stirs are always processed literally,
for example, \\\\ and \\ ".
Eod;

The result of this example:

An example of a text occupying several lines using the NOWDOC syntax. Inverse strokes are always processed literally, for example, \\\\ and \\ ".

Example # 8 Nowdoc String QUoting Example with Variables

/ * A more complex example with variables. * /
class Foo.
{
Public $ foo;
Public $ Bar;

FUNCTION __CONSTRUCT ()
{
$ this -\u003e foo \u003d "foo";
$ this -\u003e bar \u003d array ("Bar1", "Bar2", "Bar3");
}
}

$ foo \u003d new foo ();
$ name \u003d "name";

echo.<<<"EOT"
My name is "$ Name". I type $ foo-\u003e foo.
Now I type ($ Foo-\u003e Bar).
This should not withdraw the title "A": \\ x41
EOT;
?>

The result of this example:

My name is "$ Name". I type $ foo-\u003e foo. Now I type ($ Foo-\u003e Bar). This should not withdraw the title "A": \\ x41

Example # 9 Example of using static data

class foo (
Public $ Bar \u003d<<<"EOT"
bar
EOT;
}
?>

Comment:

NOWDOC support has been added to PHP 5.3.0.

Processing of variables

If the string is specified in double quotes, or with HEREDOC, variables inside it are processed.

There are two types of syntax: simple and complex. Simple syntax is easier and convenient. It allows the variable processing, the value of the array ( array.) or object properties ( object.) with a minimum effort.

Complex syntax can be determined on curly brackets surrounding the expression.

Simple syntax

If the interpreter meets the dollar sign ( $ ), it captures so many characters as it is possible to form the correct name of the variable. If you want to accurately define the end of the name, conclude a variable name in curly brackets.

$ juice \u003d "apple";

echo "He Drank Some $ JUICE JUICE." . Php_eol;

// incorrectly. "S" is a faithful character for the variable name, but the variable has the name $ juice.
eCHO "HE DRANK SOME JUICE MADE OF $ JUICES." ;

// Correctly. Strictly listed End of the variable name using brackets:
eCHO "HE DRANK SOME JUICE MADE OF $ (Juice) s." ;
?>

The result of this example:

HE DRANK SOME Apple Juice. HE DRANK SOME JUICE MADE OF. HE DRANK SOME JUICE MADE OF APPLES.

An array element can be processed similarly ( array.) or object property ( object.). In the indexes of the array closing square bracket ( ] ) Indicates the end of the definition of the index. For the properties of the object, the same rules apply as for simple variables.

Example # 10 example simple syntax

define ("Koolaid", "koolaid1");
$ juices \u003d array ("Apple", "Orange", "koolaid1" \u003d\u003e "Purple");

echo "He Drank Some $ Jices [0] Juice." . Php_eol;
eCHO "HE DRANK SOME $ JIICES [1] JUICE." . Php_eol;
eCHO "HE DRANK SOME $ JUICES [Koolaid1] Juice." . Php_eol;

class PEOPLE (
Public $ John \u003d "John Smith";
Public $ jane \u003d "jane smith";
Public $ robert \u003d "robert paulsen";

Public $ smith \u003d "smith";
}

$ people \u003d new people ();

echo "$ PEOPLE -\u003e John Drank Some $ Jices [0] Juice." . Php_eol;
echo "$ PEOPLE -\u003e John Then Said Hello to $ PEOPLE -\u003e Jane." . Php_eol;
echo "$ PEOPLE -\u003e John" S Wife Greeted $ People -\u003e Robert. "PHP_EOL;
echo "$ PEOPLE -\u003e Robert Greeted The Two $ People -\u003e Smiths." ; // not work
?>

The result of this example:

HE DRANK SOME Apple Juice. HE DRANK SOME ORANGE JUICE. HE DRANK SOME PURPLE JUICE. John Smith Drank Some Apple Juice. John Smith Then Said Hello to Jane Smith. John Smith "S Wife Greeted Robert Paulsen. Robert Paulsen Greeted The Two.

PHP 7.1.0 Added support negative numeric indexes.

Example # 11 Negative Numeric Indices

$ String \u003d "String";
echo. "Symbol with index -2 is equal$ String [- 2]. ", PHP_EOL;
$ string [- 3] \u003d "O";
echo. "Changing the symbol in position -3 on" O "gives the following string:$ String. ", PHP_EOL;
?>

The result of this example:

The symbol with index -2 is n. Changing the symbol in position -3 on "O" gives the following line: Strong

For something more complex, use complex syntax.

Complex (figured) syntax

It is called difficult because it is difficult in understanding, but because it allows you to use complex expressions.

Any scalar variable, an array element or an object property displayed in a string can be presented in the line by this syntax. Just write down the expression as well as outside the line, and then enter it into { and } . Insofar as { can not be shielded, this syntax will be recognized only when $ Should be directly from { . Use {\$ to print {$ . Several explanatory examples:

// Show all the errors
error_Reporting (E_ALL);

$ Great \u003d "Great";

// does not work, displays: it (great)
echo "This ($ Great)";

// works, displays: it's great
echo "This ($ Great)";

// Works
echo. "This width square($ SQUARE -\u003e WIDTH) 00 centimeters. ";

// Works, keys enclosed in quotes, work only with figure bracket syntax
echo "It works: ($ ARR [" KEY "])";

// Works
echo "It works: ($ Arr [4] [3])";

// It is incorrect for the same reason as $ foo outside
// Lines. In other words, it will still work,
// But since PHP is first looking for a Foo constant, it will cause
// Error level E_NOTICE (indefinite constant).
echo. "It is not right:($ Arr [Foo] [3]) ";

// Works. When using multidimensional arrays inside
// Lines Always use curly brackets
echo "It works: ($ ARR [" FOO "] [3])";

// Works.
echo "It works:". $ arr ["foo"] [3];

echo. "It also works:($ OBJ -\u003e VALUES [3] -\u003e Name) ";

echo. "This is the value of a variable named$ Name: ($ ($ Name)) ";

echo. "This is the value of a variable by name that returns the getName () function:($ (getName ())) ";

echo. "This is the value of a variable by name that returns \\ $ Object-\u003e getName ():($ ($ Object -\u003e getName ())) ";

// does not work, displays: This is what returns getName (): (getName ())
echo. "This is what returns getName (): (getName ())";
?>

With this syntax, it is also possible to access the properties of the object inside the lines.

class foo (
VAR $ Bar \u003d "I Am Bar." ;
}

$ foo \u003d new foo ();
$ Bar \u003d "Bar";
$ BAZ \u003d Array ("Foo", "Bar", "Baz", "Quux");
echo "($ foo -\u003e $ bar) \\ n";
echo "($ foo -\u003e ($ BAZ [1])) \\ n";
?>

The result of this example:

I am bar. I am bar.

Comment:

Functions, calls of methods, static class variables, as well as classes constants running inside {$} Starting with the PHP version 5. However, the specified value will be processed as the name of the variable in the same context as the string in which it is determined. Using single curly braces ( {} ) It will not work to access the values \u200b\u200bof the functions, methods, class constants or static variables.

// Show all the errors
error_Reporting (E_ALL);

class Beers (
const softdrink \u003d "rootbeer";
Public Static $ Ale \u003d "IPA";
}

$ rootbeer \u003d "A & W";
$ ipa \u003d "alexander keith \\" s ";

// It works, displays: I would like A & W
echo "I would like ($ (beers :: softdrink)) \\ n";

// it works too, displays: I would like Alexander Keith "s
echo "I would like $ (Beers :: $ ALE)) \\ n";
?>

Access to the symbol in the string and its change

Symbols in lines can be used and modified by defining their offset relative to the beginning of the string, starting from scratch, in square brackets after a string, for example, $ STR. Think about the line for this purpose, as an array of characters. If you need to get or replace more than 1 symbol, you can use functions substr () and substr_replace ().

Comment: Starting with PHP 7.1.0, negative displacement values \u200b\u200bare supported. They define offset from the end of the line. Previously, negative offset caused a level error E_NOTICE When reading (returning an empty string) or E_warning When recording (leaving the string unchanged).

Comment: The symbol in the row can also be treated with curly brackets, for example, $ STR (42).

Attention

Attempting to write to the offset over the boundaries of the string will complement the string with spaces before this offset. Neum types will be converted to whole. Invalid displacement type will cause a level error E_warning. Only the first symbol of the row is used. Starting with PHP 7.1.0, the assignment of an empty string will cause a fatal error. In this case, the zero byte (NULL) was assigned.

Attention

Rows in PHP internally represent byte arrays. As a result, access or change in the displacement string is unsafe in terms of multibyte encoding, and should be performed only with strings in single-byte encodings, such as, for example, ISO-8859-1.

Comment: Starting with PHP 7.1.0, the use of an empty index causes a fatal error, earlier in this case the string was transformed into an array without warning.

Example # 12 Multiple Row Examples

// Get the first character string symbol
$ str \u003d "this is a test." ;
$ first \u003d $ str [0];

// Get the Third String Symbol
$ third \u003d $ str [2];

// Get the last character string symbol
$ str \u003d "This is Still A Test." ;
$ Last \u003d $ str [STRLEN ($ ST) - 1];

// Changing the last character string symbol
$ str \u003d "Look AT The Sea";
$ STR [STRLEN ($ STR) - 1] \u003d "E";

?>

Starting with PHP 5.4, the offset in the string should be set either an integer or a string containing numbers, otherwise a warning will be issued. Previously offset, specified row of type "FOO", without warnings, was transformed into 0 .

Example # 13 differences between PHP 5.3 and PHP 5.4

$ str \u003d "ABC";

VAR_DUMP ($ str ["1"]);
vAR_DUMP (ISSET ($ STR ["1"]));

VAR_DUMP ($ STR ["1.0"]);
vAR_DUMP (ISSET ($ STR ["1.0"]));

VAR_DUMP ($ str ["x"]);
vAR_DUMP (ISSET ($ STR ["X"]));

Var_dump ($ str ["1x"]);
vAR_DUMP (ISSET ($ STR ["1X"]));
?>

The result of this example in PHP 5.3:

string (1) "B" BOOL (TRUE) STRING (1) "B" BOOL (TRUE) STRING (1) "A" BOOL (TRUE) STRING (1) "B" BOOL (TRUE)

The result of this example in PHP 5.4:

string (1) "B" BOOL (TRUE) WARNING: ILLEGAL STRING OFFSET "1.0" in /tmp/t.php on line 7 String (1) "B" BOOL (FALSE) WARNING: ILLEGAL STRING OFFSET "X" IN / TMP / T.PHP ON LINE 9 STRING (1) "A" BOOL (FALSE) STRING (1) "B" BOOL (FALSE)

Comment:

An attempt to access the variables of other types (excluding arrays or objects that implement certain interfaces) with or {} silently return NULL.

Comment:

PHP 5.5 added support for access to symbols in string literals using syntax or {} .

For modifying strings, there are many useful features.

The main functions are described in the section of string functions, and for extended search and replacement - the functions of perl-compatible regular expressions.

Convert to string

The value can be transformed into a string by bringing (String)or functions strval (). In expressions where the string is necessary, the conversion occurs automatically. This happens when you use functions. echo. or printOr when the value of the variable is compared with the string. Reading the sections of the Types and manipulation of types will make the following more understandable. see also sETTYPE ().

Arrays are always transformed into a string "Array"so you can't display the contents of the array ( array.) Using echo. or printTo find out what it contains. To view a separate item, use something like echo $ Arr ["Foo"]. See below Tips on how to display / view all content.

To convert a variable type "Object" in type string Used magic method __tostring.

Value NULL Always converted to an empty string.

As you could see above, direct conversion into the string of arrays, objects or resources does not give any useful information about the values \u200b\u200bthemselves, except for their types. A more suitable way to output values \u200b\u200bfor debugging - use functions print_R () and vAR_DUMP ().

Most values \u200b\u200bin PHP can be transformed into a string for constant storage. This method is called serialization and can be performed using a function. sERIALIZE ().

Row conversion in numbers

If the string is recognized as a numeric value, the resulting value and the type is defined as shown below.

If the string does not contain any of the characters ".", "E", or "E", and the value of the number is placed within the limits of integers (defined Php_int_max), the string will be recognized as an integer ( integer). In all other cases, it is considered a floating point number ( float.).

The value is determined by the initial part of the line. If the string begins with a correct numeric value, this value will be used. Otherwise, the value will be 0 (zero). The right numeric value is one or more digits (which can contain a decimal point), at the request of the sign presented with the subsequent optional indicator. The degree indicator is "E" or "E" with subsequent one or more numbers.

$ Foo \u003d 1 + "10.5"; // $ foo is Float (11.5)
$ Foo \u003d 1 + "-1.3e3"; // $ foo is Float (-1299)
$ Foo \u003d 1 + "Bob-1.3E3"; // $ foo is Integer (1)
$ Foo \u003d 1 + "Bob3"; // $ foo is Integer (1)
$ Foo \u003d 1 + "10 Small Pigs"; // $ foo is Integer (11)
$ Foo \u003d 4 + "10.2 Little Piggies"; // $ foo is Float (14.2)
$ Foo \u003d "10.0 PIGS" + 1; // $ foo is Float (11)
$ Foo \u003d "10.0 PIGS" + 1.0; // $ foo is Float (11)
?>

For more information on this conversion, see the UNIX StrTod (3) documentation section.

If you want to test any of the examples of this section, copy and paste it and the next line to see what happens:

echo "\\ $ Foo \u003d\u003d $ Foo; Type:". GetType ($ foo). "
\\ n ";
?>

Do not expect to obtain a symbol code by converting it to an integer (as is done, for example, in C). To convert the characters to their ASCII codes and use the functions back oRD () and chr ().

Details of the implementation of a string type

7 Years Ago.

The Documentation Does Not Mention, But a Closing Semicolon AT The End of the Heredoc Is Actually Interpreted As A Real Semicolon, And As Such, Sometimes Leads to Syntax Errors.

$ Foo \u003d.<<abcd.
End;
?>

This Does Not:

foo (<<abcd.
End;
);
// Syntax Error, UnexPected ";"
?>

Without Semicolon, IT Works Fine:

foo (<<abcd.
End.
);
?>

3 Years Ago.

You can use String Like Array of Char (Like C)

$ a \u003d "String Array Test";

vAR_DUMP ($ A);
// RETURN STRING (17) "STRING ARRAY TEST"

vAR_DUMP ($ A);
// Return String (1) "S"

// - WITH ARRAY CAST -
vAR_DUMP ((Array) $ A);
// Return Array (1) (\u003d String (17) "String Array Test")

vAR_DUMP ((Array) $ A);
// Return String (17) "S"

Norihiori.

15 YEARS AGO.

You can Use the Complex Syntax to Put The Value of Both Object Properties and Object Methods Inside A String. For example ...
class Test (
Public $ one \u003d 1;
Public Function Two () (
Return 2;
}
}
$ test \u003d new test ();
echo "foo ($ test -\u003e one) bar ($ test -\u003e two ())";
?>
Will Output "Foo 1 Bar 2".

HOWEVER, YOU CANNOT DO THIS FOR ALL VALUES IN YOUR NAMESPACE. Class Constants and Static Properties / Methods Will Not Work Because The Complex Syntax Looks for the "$".
class Test (
Const One \u003d 1;
}
echo "Foo (Test :: One) Bar";
?>
This Will Output "Foo (Test :: One) Bar." Constants and Static Properties Require You to Break Up the String.

3 Years Ago.

BEWARE THAT CONSISTENT WITH "STRING Conversion to Numbers":

If ("123ABC" \u003d\u003d 123) ECHO "(INTSTR \u003d\u003d INT) Incorrectly Tests AS TRUE.";

// Because One Side Is a Number, The String IS Incorrectly Converted from Intstr to Int, Which Then Matches The Test Number.

// True for all Conditionals Such AS If and Switch States (Probably Also While Loops)!

// This Could Be a Huge Security Risk When Testing / USING / Saving User Input, While Expeted and Testing for Only An Integer.

// IT Sems The Only Fix IS for 123 to Be A String AS "123" SO No Conversion Happens.

?>

6 YEARS AGO.

LEADING ZEROES IN STRINGS ARE (Least-surprise) Not treated as Octal.
Consider:
$ x \u003d "0123" + 0;
$ y \u003d 0123 + 0;
echo "x is $ x, y is $ y"; // Prints "X IS 123, Y IS 83"
iN OTHER WORDS:
* LEADING ZEROS IN NUMERIC LITERALS IN THE SOURCE-CODE ARE INTERPRETED AS "OCTAL", C.F. STRTOL ().
* Leading Zeros in Strings (EG User-Submitted Data), WHEN CAST (Implicitly or Explicitly) to Integer Are Ignored, and Considered As Decimal, C.F. StrTod ().

10 Years Ago.

Here IS An Easy Hack to Allow Double-quoted Strings and Heredocs to Contain Arbitrary Expressions in Curly Braces Syntax, Including Constants and Other Function Calls:

// Hack Declaration
fUNCTION _EXPR ($ V) (Return $ V;)
$ _EXPR \u003d "_Expr";

// Our Playground.
define ("QWE" , "ASD");
define.("ZXC", 5 );

$ A.= 3 ;
$ B.= 4 ;

function. c.($ A., $ B.) (Return.$ A.+ $ B.; }

// usage
echo."Pre.{ $ _Expr.(1 + 2 )} POST \\ N "; // Outputs "PRE 3 POST"
echo."Pre.{ $ _Expr.(qWE.)} POST \\ N "; // Outputs "Pre ASD POST"
echo."Pre.{ $ _Expr.(c.($ A., $ B.)+ zxc.* 2 )} POST \\ N "; // Outputs "PRE 17 POST"

// GENERAL SYNTAX IS ($ _EXPR (...))
?>

2 Years Ago.

I Though That It Would BE Helpful to Add This Comment So That The Information At Least Appears on the Right Page on the php site.

Note That If You Intend To Use A Double-quoted String with An Associative Key, You may be into the t_encapsed_and_whiteespace error. Some Regard This As One of the Less Obvious Error Messages.

An Expression SUCH AS:

$ Fruit.\u003d array (
"A"=> "Apple",
"B"=> "BANANA",
// etc.
);

Print. "This is a$ Fruit.[ "A"] "; // T_ENCAPSED_AND_WHITESPACE.
?>

will Definitely Fall to Pieces.

You can RESOLVE IT AS FOLLOWS:

print"This is a$ Fruit.[ a.] " ; // Unquote The Key
print"This is a${ fruit.[ "A"]} " ; // Complex Syntax
print"This is a{ $ Fruit.[ "A"]} " ; // COMPLEX SYNTAX VARIATION
?>

I Have a Personal Preference for The Last Variation As It Is More Natural and Closer to What The Expression Would be Like Outside The String.

IT's Not Clear (To Me, At Least) Why PHP Missinterprets The Single Quote Inside The Expression But I Imagine That It Has Something To Do With the Fact QUOTES ARE NOT PART OF THE VALUE STRING - ONCE THE STRING IS ALREADY BEING PARSED THE QUOTES JUST Get In the Way ...?

2 Years Ago.

Both Should Work :(

classTesting.{
Public Static.$ Var.= "Static";
Public Const Var \u003d"Const";

Public Function. sayhellostatic.() {
Echo."Hello:{ $ THIS:: $ Var.} " ;
}

Public Function. sayhelloconst.() {
Echo."Hello:{ $ THIS:: var)" ; // Parse Error: Syntax Error, UnExpected ")", Expecting "["
}
}

$ OBJ.\u003d NEW.Testing.();
$ OBJ.-> sayhellostatic.();
$ OBJ.-> sayhelloconst.();

3 Years Ago.

Something I Experiened Which No Doubt Will Help Someone. . .
In My Editor, This Will Syntax Highlight Html and The $ Comment:

$ HTML \u003d.<<<"EOD"
$ comment
Eod;

USING THIS SHOWS ALL THE SAME COLOR:

$ HTML \u003d.<<$ comment
Eod;

mAKING IT A LOT EASIER TO WORK WITH

11 Years Ago.

To Save Your Mind Don "T Read Previous Comments About Dates;)

WHEN BOT STRINGS CAN BE CONVERED TO THE NUMERICS (IN ("$ A"\u003e "$ B") Test) Then Resulted Numerics Are Used, Else Full Strings Are Compared Char-by-Char:

var_Dump("1.22" > "01.23" ); // BOOL (FALSE)
var_Dump("1.22.00" > "01.23.00" ); // BOOL (TRUE)
var_Dump("1-22-00" > "01-23-00" ); // BOOL (TRUE)
var_Dump((Float)"1.22.00" \u003e (Float)"01.23.00" ); // BOOL (FALSE)
?>

Rows in PHP are framed by single or double quotes. The main difference is that in double quotes can be substituted with a variable:

Now we can come up with another solution to the task of the lesson variables in PHP:

$ title"; Echo"

"; ?>

How does PHP find a variable in the string?

Everything is simple. Remember what characters can be used in the name of the variable? These are numbers, letters and emphasising _.

Here is PHP and accepts for the name everything is between the $ symbol and the first forbidden symbol.

In the following PHP code, it will incorrectly determine the name of the variable and give an error:

Result in the browser:

Notice: undefined Variable: Priceurb in D: \\ OpenServer \\ Domains \\ site \\ index.php on line 3

To PHP correctly determined the name of the variable in the string, you need to place it in curly brackets ():

Result in the browser:

1499rub

There is no unambiguous opinion, what quotes need to be used for ordinary lines in which nothing needs to be substituted. However, many programmers prefer to use single quotes.

The fact is that dual quotes from many cause the association "to this line should substitute something." Therefore, I recommend using single quotes for ordinary text, and double - only when you need to substitute the variable in the text. Example:

Shielding quotes

If you need to put quotes inside the string, there are 2 ways to do it:

In the second example, the reverse layer \\ shields the quotes next after it so that PHP perceived it as a string.

What do you think you need to do to display only the reverse slash? After all, it will shield a closing quotation. It's funny, but you need to write a second slash to shielding the first:

Tabulation and transfer of string in double quotes

The reverse layer in double quotes allows you to shield not only quotes and yourself, but also some other characters. The most popular of them is a tab (the long space that you get when you press Tab) and the transfer of the string. They look like this:

Write a script that:
1. Creates a $ Type variable with a game value.
2. Creates a variable $ Name with the "World of Warcraft" value (with quotes).
3. Displays both variables inside the tag

. There must be a space between the variables.

What kind of quotes use to design strings - apostrophes or classic double quotes?

Let's analyze the difference between double and single quotes in PHP, and on examples, find out when you need to use.

Variables and shielding sequences for special characters encountered in lines enclosed in single quotes are not processed. The lines framed by apostrophes are processed by the PHP interpreter much faster than similar lines surrounded by double quotes.

The reason here is simple: Lines in dual quotes Interpreter PHP additionally checks for variables and if these are located, then instead of the variable name in the string inserts its value. But the string concluded in the apostrophes is perceived by the interpreter as ordinary text and no transformations in these PHP lines does not conduct. I think it is clear that the processing of lines in single quotes in any case will occur faster.

To begin with, we describe how to determine the string, and then check how faster the rows in single quotes will occur.

The easiest way to determine the string is to conclude it into single quotes ("). In order to use single quotes inside the string enclosed in single quotes, they need to be ahead of the reverse deficent (\\) symbol, that is shielded. If the reverse sink Must go before a single quotation or being at the end of the line, you need to duplicate it. If you try to shield any other character, the reverse sinking feature will also be printed.

We give an example of using single quotes:
// Remove: Simple String
echo "Simple Row";
// Removes: i "M Here
echo "I \\" M Here ";
// Will out: it will not insert: \\ N new string
echo "It will not insert: \\ N new string";
// Will out: the $ sample variable will also not substitute
echo "$ Example variable will not substitute either"; If the string is enclosed in double quotes ("), PHP recognizes more control sequences for special characters and also substitutes instead of the variable name in the string of its value. Just as with single quotes, in order to use double quotes inside a string concluded. In double quotes, they must be ahead with a symbol of the reverse braid (\\).

Let us give an example of using double quotes:
// Remove: Simple String
echo "Simple Row";
// Will out: firm "Snowdrop" "
echo "Firm \\" Snowdrophry \\ "";
// Will out: it will translate to a new string
echo "It will translate to the new line \\ n";
// Will out: the variable will substitute
$ example \u003d "substitut";
echo "Variable $ Example"; It should also be remembered that the sequence "\\ n" (new line), "\\ r" (return carriage) for ordinary text, and not for HTML. So in the browser you will not see changes (only in the source page of the page).

Let's find out how faster than single quotes of double. For measurements, write a short test script, and immediately note that if you have it to test it, the results that depend on the hardware of your PC or server will be different.
// Return the time stamp at the beginning of the cycle
$ START \u003d Microtime (True);
// Create a cycle cycle for 1 million iterations
for ($ i \u003d 0; $ i< 1000000; $i++) {
$ Text \u003d "Here is a symbol string";
}
// Calculate the time spent
$ TIME \u003d (Microtime (True) - $ Start); Result: 0.09 seconds.

If we replace single quotes on double:
$ Text \u003d "Here is a symbol string"; The result will be equal to 0.10 seconds.

As we see, when using text lines, the difference in time of execution is very small, it can even be said and does not exist at all. The most interesting will begin when we try to combine the string and variable.
$ Text \u003d "Here is the symbol line $ i"; or
$ text \u003d $ i. "Here is a symbolic string"; The result is approximately: 0.27 seconds.

The difference is very sensitive. Concatenation and dual quotes clearly affect the speed if variables are added to the string.

When the server processes the code, it checks all the contents of dual quotes for variables, constants and other. It takes time. And the fact that there is between single quotes The server processes as the finished text and it does not care what is located there. The difference between the speed of single and double quotes is very insignificant, but if you develop a highly loaded project, somewhat saved milliseconds are already a victory.