Question

What is an anonymous function in PHP? Could you give me a simple example, please?

Answer 1

PHP.net has a manual page about Anonymous functions and on Wikipedia you can read about Anonymous functions in general.

Anonymous functions can be used to contain functionality that need not be named and possibly for short-term use. Some notable examples include closures.

Example from PHP.net

<?php
$greet = function($name)
{
    printf("Hello %s\r\n", $name);
};

$greet('World');
$greet('PHP');
?>

PHP 4.0.1 to 5.3

$foo = create_function('$x', 'return $x*$x;');
$bar = create_function("\$x", "return \$x*\$x;");
echo $foo(10);

PHP 5.3

$x = 3;
$func = function($z) { return $z *= 2; };
echo $func($x); // prints 6

PHP 5.3 does support closures but the variables must be explicitly indicated

$x = 3;
$func = function() use(&$x) { $x *= 2; };
$func();
echo $x; // prints 6

Examples taken from Wikipedia and php.net