{"id":130,"date":"2021-03-08T00:26:11","date_gmt":"2021-03-08T00:26:11","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=130"},"modified":"2025-04-06T07:31:40","modified_gmt":"2025-04-06T07:31:40","slug":"php-array-filter","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-tutorial\/php-array-filter\/","title":{"rendered":"PHP array_filter Function"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the PHP array_filter()<\/code> function to filter elements of an array using a callback function.<\/p>\n\n\n\n

Introduction to PHP array_filter() function #<\/a><\/h2>\n\n\n\n

When you want to filter elements of an array<\/a>, you often iterate over the elements<\/a> and check whether the result array should include each element.<\/p>\n\n\n\n

The following example uses the foreach<\/a><\/code> statement to iterate over the elements of the $numbers<\/code> array and filter the odd numbers:<\/p>\n\n\n

<?php<\/span>\n\n$numbers = [1<\/span>, 2<\/span>, 3<\/span>, 4<\/span>, 5<\/span>];\n$odd_numbers = [];\n\nforeach<\/span> ($numbers as<\/span> $number) {\n\tif<\/span> ($number % 2<\/span> === 1<\/span>) {\n\t\t$odd_numbers[] = $number;\n\t}\n}\n\nprint_r($odd_numbers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span>\n(\n    [0<\/span>] => 1<\/span>\n    [1<\/span>] => 3<\/span>\n    [2<\/span>] => 5<\/span>\n)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The array_filter()<\/code> function makes the code less verbose and more expressive:<\/p>\n\n\n
<?php<\/span>\n\n$numbers = [1<\/span>, 2<\/span>, 3<\/span>, 4<\/span>, 5<\/span>];\n\n$odd_numbers = array_filter(\n\t$numbers,\n\tfunction<\/span> ($number)<\/span> <\/span>{\n\t\treturn<\/span> $number % 2<\/span> === 1<\/span>;\n\t}\n);\n\nprint_r($odd_numbers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
From PHP 7.4, you can use the arrow function<\/a> instead of the anonymous function like this:<\/p>\n\n\n
<?php<\/span>\n\n$numbers = [1<\/span>, 2<\/span>, 3<\/span>, 4<\/span>, 5<\/span>];\n\n$odd_numbers = array_filter(\n\t$numbers,\n\tfn ($number) => $number % 2<\/span> === 1<\/span>\n);\n\nprint_r($odd_numbers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The array_filter()<\/code> function allows you to filter elements of an array using a callback function.<\/p>\n\n\n\n
The following illustrates the syntax of the array_filter()<\/code> function:<\/p>\n\n\n
array_filter ( \n    array<\/span> $array , \n    callable|null<\/span> $callback = null<\/span> , \n    int $mode = 0<\/span> \n) : array<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The array_filter()<\/code> function iterates over the elements of the $array<\/code> and passes each element to the $callback<\/code> function. If the callback function returns true<\/code>, the array_filter()<\/code> function includes the element in the result array.<\/p>\n\n\n\n
Basic array_filter() function example #<\/a><\/h2>\n\n\n\n
To filter out all the odd numbers in the $numbers<\/code> array, you use the array_filter()<\/code> function as follows:<\/p>\n\n\n
<?php<\/span>\n\n$numbers = [1<\/span>, 2<\/span>, 3<\/span>, 4<\/span>, 5<\/span>];\n\n$even_numbers = array_filter(\n\t$numbers,\n\tfunction<\/span> ($number)<\/span> <\/span>{\n\t\treturn<\/span> $number % 2<\/span> === 0<\/span>;\n\t}\n);\n\nprint_r($even_numbers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span> ( [1<\/span>] => 2<\/span> [3<\/span>] => 4<\/span> )<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Using callback as a method of a class #<\/a><\/h2>\n\n\n\n
Besides a callback, you can pass a method of a class to the array_filter()<\/code> function like this:<\/p>\n\n\n
array_filter($items,[$instance,'callback'<\/span>]);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
For example:<\/p>\n\n\n
class<\/span> Odd<\/span>\n<\/span>{\n    public<\/span> function<\/span> isOdd<\/span>($num)<\/span>\n    <\/span>{\n        return<\/span> $num % 2<\/span> === 1<\/span>;\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The Odd<\/code> class has a method isOdd()<\/code> that returns true<\/code> if the argument is an odd number; otherwise, it returns false<\/code>.<\/p>\n\n\n\n
To use the isOdd()<\/code> method as the callback of the array_filter()<\/code> function, you use the following form:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Odd<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> isOdd<\/span>($num)<\/span>\n\t<\/span>{\n\t\treturn<\/span> $num % 2<\/span> === 1<\/span>;\n\t}\n}\n\n$numbers = [1<\/span>, 2<\/span>, 3<\/span>, 4<\/span>, 5<\/span>];\n$odd_numbers = array_filter(\n\t$numbers,\n\t[new<\/span> Odd(), 'isOdd'<\/span>]\n);\n\nprint_r($odd_numbers);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span> ( [0<\/span>] => 1<\/span> [2<\/span>] => 3<\/span> [4<\/span>] => 5<\/span> )<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
array_filter($array, ['Class'<\/span>,'callback'<\/span>]);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Even<\/span>\n<\/span>{\n    public<\/span> static<\/span> function<\/span> isEven<\/span>($num)<\/span>\n    <\/span>{\n        return<\/span> $num % 2<\/span> === 0<\/span>;\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The Even<\/code> class has a static method isEven()<\/code> that returns true<\/code> if the argument is even; otherwise, it returns false<\/code>.<\/p>\n\n\n\n
The following uses the isEven()<\/code> static method as the callback of the array_fitler()<\/code> function:<\/p>\n\n\n
$even_numbers = array_filter($numbers, ['Even'<\/span>,'isEven'<\/span>]);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
<?php<\/span>\n\nclass<\/span> Positive<\/span>\n<\/span>{\n    public<\/span> function<\/span> __invoke<\/span>($number)<\/span>\n    <\/span>{\n        return<\/span> $number  > 0<\/span>;\n    }\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the Positive<\/code> class has the __invoke()<\/code> magic method that returns true<\/code> if the argument is positive; otherwise, it returns false.<\/p>\n\n\n\n
You can pass an instance of the Positive<\/code> class to the array_filter()<\/code> function for including only positive numbers in the result array.<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> Positive<\/span>\n<\/span>{\n\tpublic<\/span> function<\/span> __invoke<\/span>($number)<\/span>\n\t<\/span>{\n\t\treturn<\/span> $number > 0<\/span>;\n\t}\n}\n\n$numbers = [-1<\/span>, -2<\/span>, 0<\/span>, 1<\/span>, 2<\/span>, 3<\/span>];\n$positives = array_filter($numbers, new<\/span> Positive());\n\nprint_r($positives);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span>\n(\n    [3<\/span>] => 1<\/span>\n    [4<\/span>] => 2<\/span>\n    [5<\/span>] => 3<\/span>\n)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Passing elements to the callback function #<\/a><\/h2>\n\n\n\n
By default, the array_filter()<\/code> function passes the value of each array element to the callback function for filtering.<\/p>\n\n\n\n
Sometimes, you want to pass the key, not the value, to the callback function. In this case, you can pass ARRAY_FILTER_USE_KEY<\/code> as the third argument of the array_filter()<\/code> function. For example:<\/p>\n\n\n
<?php<\/span>\n\n$inputs = [\n\t'first'<\/span> => 'John'<\/span>,\n\t'last'<\/span> => 'Doe'<\/span>,\n\t'password'<\/span> => 'secret'<\/span>,\n\t'email'<\/span> => 'john.doe@example.com'<\/span>\n];\n\n$filtered = array_filter(\n\t$inputs,\n\tfn ($key) => $key !== 'password'<\/span>,\n\tARRAY_FILTER_USE_KEY\n);\n\nprint_r($filtered);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span>\n(\n    [first] => John\n    [last] => Doe\n    [email] => john.doe@example.com\n)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, $filtered<\/code> contains all elements of the $inputs<\/code> array except for the element whose key is password<\/code>.<\/p>\n\n\n\n
To pass both the key and value of the element to the callback function, you pass the ARRAY_FILTER_USE_BOTH<\/code> value as the third argument of the array_filter()<\/code> function. For example:<\/p>\n\n\n
<?php<\/span>\n\n$inputs = [\n\t'first'<\/span> => 'John'<\/span>,\n\t'last'<\/span> => 'Doe'<\/span>,\n\t'password'<\/span> => 'secret'<\/span>,\n\t'email'<\/span> => ''<\/span>\n];\n\n$filtered = array_filter(\n\t$inputs,\n\tfn ($value, $key) => $value !== ''<\/span> && $key !== 'password'<\/span>,\n\tARRAY_FILTER_USE_BOTH\n);\n\nprint_r($filtered);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Array<\/span>\n(\n    [first] => John\n    [last] => Doe\n)<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this tutorial, you have learned how to use the PHP array_filter()<\/code> function to filter elements of an array using a callback.<\/p>\n
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Did you find this tutorial useful?<\/div>\n\t\t
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Try it<\/a><\/p>\n\n\n\n
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From PHP 5.3, if a class<\/a> implements the __invoke()<\/a><\/code> magic method<\/a>, you can use it as a callable. For example:<\/p>\n\n\n
If you have a class that has is a static method<\/a>, you pass the static method as the callback of the array_filter()<\/code> function:<\/p>\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
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