String: Syntax

A string literal can be specified in four different ways.

<?php
echo 'this is a simple string';

echo 'You can also have embedded newlines in
strings this way as it is
okay to do';

// Outputs: Arnold once said: "I'll be back"
echo 'Arnold once said: "I\'ll be back"';

// Outputs: You deleted C:\*.*?
echo 'You deleted C:\\*.*?';

// Outputs: You deleted C:\*.*?
echo 'You deleted C:\*.*?';

// Outputs: This will not expand: \n a newline
echo 'This will not expand: \n a newline';

// Outputs: Variables do not $expand $either
echo 'Variables do not $expand $either';
?>

The simplest way to specify a string is to enclose it in single quotes (the character ').

Unlike the double-quoted and heredoc syntaxes, variables and escape sequences for special characters will not be expanded when they occur in single quoted strings.

If the string is enclosed in double-quotes ("), PHP will interpret the following escape sequences for special characters.

The most important feature of double-quoted strings is the fact that variable names will be expanded.

<?php
$str = <<<EOD
Example of string
spanning multiple lines
using heredoc syntax.
EOD;

/* More complex example, with variables. */
class foo
{
    var $foo;
    var $bar;

    function __construct()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<EOT
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should print a capital 'A': \x41
EOT;
?>

My name is "MyName". I am printing some Foo.
Now, I am printing some Bar2.
This should print a capital 'A': A

<?php
// Static variables
function foo()
{
    static $bar = <<<LABEL
Nothing in here...
LABEL;
}

// Class properties/constants
class foo
{
    const BAR = <<<FOOBAR
Constant example
FOOBAR;

    public $baz = <<<FOOBAR
Property example
FOOBAR;
}
?>

<?php
echo <<<"FOOBAR"
Hello World!
FOOBAR;
?>

• A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.
• The closing identifier must begin in the first column of the line.
• Heredoc text behaves just like a double-quoted string, without the double quotes.
• Quotes in a heredoc do not need to be escaped.
• Variables are expanded, but the same care must be taken when expressing complex variables inside a heredoc as with strings.

<?php
echo <<<'EOD'
Example of string spanning multiple lines
using nowdoc syntax. Backslashes are always treated literally,
e.g. \\ and \'.
EOD;

Example of string spanning multiple lines
using nowdoc syntax. Backslashes are always treated literally,
e.g. \\ and \'

<?php
class foo
{
    public $foo;
    public $bar;

    function __construct()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<'EOT'
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': \x41
EOT;
?>

My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': \x41

<?php
class foo {
    public $bar = <<<'EOT'
bar
EOT;
}
?>

• Nowdocs are to single-quoted strings what heredocs are to double-quoted strings.
• A nowdoc is specified similarly to a heredoc, but no parsing is done inside a nowdoc.
• The construct is ideal for embedding PHP code or other large blocks of text without the need for escaping.
• It shares some features in common with the SGML &lt;![CDATA[ ]]&gt; construct, in that it declares a block of text which is not for parsing.
• A nowdoc is identified with the same <<< sequence used for heredocs, but the identifier which follows is enclosed in single quotes, e.g. <<<'EOT'.
• All the rules for heredoc identifiers also apply to nowdoc identifiers, especially those regarding the appearance of the closing identifier.