Anonymous Function in PHP

Last Updated : 27 Oct, 2026

An anonymous function in PHP is a function without a name, typically assigned to a variable or passed as an argument to another function.

php_anonymous_function
  • Callbacks: Pass anonymous functions to functions such as array_map().
  • Variable Capture: Access variables from the surrounding scope using the use keyword.
  • Closures: Create functions that retain access to captured variables.
  • Flexible Code: Use anonymous functions for short, specific operations without defining named functions.

Define an Anonymous Function in PHP

Use the function keyword to define an anonymous function and assign it to a variable.

PHP 
<?php
$add = function($a, $b) {
    return $a + $b;
};

echo $add(10, 20);
?>
  • $add stores the anonymous function.
  • $a and $b are parameters that receive arguments.
  • return sends the result back to the caller.
  • The semicolon after the closing brace is required when assigning the function to a variable.

Use Anonymous Functions as Callbacks

Anonymous functions can be passed directly to other functions as callbacks. For example, array_map() applies a callback to each element of an array.

PHP 
<?php
$numbers = [1, 2, 3, 4, 5];

$squared = array_map(function($n) {
    return $n ** 2;
}, $numbers);

print_r($squared);
?>
  • The anonymous function squares each number.
  • array_map() applies the callback to every element.
  • The resulting array contains the squared values.

Capture Variables Using use

Anonymous functions do not automatically inherit ordinary variables from the surrounding scope. Use the use keyword to capture them.

PHP 
<?php
$multiplier = 2;

$double = function($number) use ($multiplier) {
    return $number * $multiplier;
};

echo $double(5);
?>
  • use ($multiplier) captures the variable by value.
  • The function uses the captured value when calculating the result.
  • Changes to $multiplier outside the function after capture do not change the captured value.

Capture Variables by Reference

Use & inside the use clause to capture a variable by reference. Changes to the original variable are then visible inside the function.

PHP 
<?php
$message = "Hello";

$greeting = function() use (&$message) {
    echo $message;
};

$message = "Hi";
$greeting();
?>
  • use (&$message) captures the variable by reference.
  • The function accesses the current value of $message.
  • Updating $message outside the function affects what the function sees.

Benefits

  • Concise Code: Define small functions where they are needed.
  • Callbacks: Pass functions as arguments to other functions.
  • Variable Capture: Access surrounding variables using use.
  • Flexibility: Create one-off operations without declaring named functions.

Limitations

  • Readability: Complex anonymous functions can make code harder to understand.
  • Debugging: Nested or lengthy callbacks can make errors harder to trace.
  • Maintainability: Reusing complex logic may be clearer with a named function or class method.
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