Why does php need anonymous functions?

Anonymous functions, also called closures, allow the temporary creation of a function without a specified name. The value most commonly used as a callback function argument. Of course, there are other applications as well.

Anonymous functions are currently implemented through the Closure class.

Anonymous function example(Recommended learning: PHP programming from entry to proficiency)

<?php
echo preg_replace_callback(&#39;~-([a-z])~&#39;, function ($match) {
    return strtoupper($match[1]);
}, &#39;hello-world&#39;);
// 输出 helloWorld
?>

Closure functions can also be used as the value of variables . PHP will automatically convert this expression into an object instance of the built-in class Closure. The method of assigning a closure object to a variable is the same as the syntax of ordinary variable assignment, and a semicolon must be added at the end:

Anonymous function variable assignment example

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

$greet(&#39;World&#39;);
$greet(&#39;PHP&#39;);
?>

Closures can inherit variables from the parent scope. Any such variables should be passed in using the use language construct. Starting from PHP 7.1, such variables cannot be passed in: superglobals, $this or have the same name as parameters.

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