PHP Reference
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Quick Reference

The PHP array_filter() function filters the values of an array using a callback function, passing each value of the input array to the callback function. If the callback function returns true, the current value from input is returned into the result array. Array keys are preserved.

<?php
function test_odd($var) {
    return($var & 1);
}

$a1 = array(1, 2, 3, 4, 5);
print_r(array_filter($a1, 'test_odd'));
?>

Note

Arrays count starting from zero NOT one. So item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on.

Output

Array ( [0] => 1 [2] => 3 [4] => 5 )

Syntax

array_filter(array, callbackfunction, flag)

Parameters

ParameterDescription
arraySpecifies the array to filter (required)
callbackfunctionSpecifies the callback function to use
flagSpecifies what arguments are sent to callback

  • ARRAY_FILTER_USE_KEY - pass key as the only argument to callback (instead of the value)

  • ARRAY_FILTER_USE_BOTH - pass both value and key as arguments to callback (instead of the value)

PHP Notes:

  • When using PHP, single or double quotation marks are acceptable and work identically to one another; choose whichever you prefer, and stay consistent
  • Arrays count starting from zero NOT one; so item 1 is position [0], item 2 is position [1], and item 3 is position [2] … and so on
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