The array_filter Function

The array_filter function filters an array using a given function. The function parameter will sequentially receive the array elements, and if the function returns true for an element, it remains in the array; if it returns false, it is removed. The array will contain only those elements for which the function returns true.

If the original array is associative, its keys are preserved.

Syntax

phparray_filter(array $array, ?callable $callback = null, int $mode = 0): array

Example

Let's keep only the positive elements in the array:

php<?php
  function func($num)
  {
    if ($num >= 0) {
      return true;
    } else {
      return false;
    }
  }
  
  $arr = [1, -1, 2, -2, 3, -3];
  
  $res = array_filter($arr, 'func');
  var_dump($res);
?>

Code execution result:

php[1, 2, 3]

Example

Let's shorten the condition:

php<?php
  function func($num)
  {
    return $num >= 0;
  }
  
  $arr = [1, -1, 2, -2, 3, -3];
  
  $res = array_filter($arr, 'func');
  var_dump($res);
?>

Code execution result:

php[1, 2, 3]

Example

Let's rewrite it using an anonymous function:

php<?php
  $arr = [1, -1, 2, -2, 3, -3];
  
  $res = array_filter($arr, function($num) {
    return $num >= 0;
  });
  
  var_dump($res);
?>

Code execution result:

php[1, 2, 3]

Example

Let's rewrite it using an arrow function:

php<?php
  $arr = [1, -1, 2, -2, 3, -3];
  $res = array_filter($arr, fn($num) => $num >= 0);
  
  var_dump($res);
?>

Code execution result:

php[1, 2, 3]

See Also