Submit a Pull Request Report a Bug

    in_array

    (PHP 4, PHP 5, PHP 7, PHP 8)

    in_array — Checks if a value exists in an array

    Description

    in_array(mixed $needle, array $haystack, bool $strict = false): bool

    Searches for needle in haystack using loose comparison unless strict is set.

    Parameters

    needle

    The searched value.

    Note:

    If needle is a string, the comparison is done in a case-sensitive manner.

    haystack

    The array.

    strict

    If the third parameter strict is set to true then the in_array() function will also check the types of the needle in the haystack.

    Note:

    Prior to PHP 8.0.0, a string needle will match an array value of 0 in non-strict mode, and vice versa. That may lead to undesireable results. Similar edge cases exist for other types, as well. If not absolutely certain of the types of values involved, always use the strict flag to avoid unexpected behavior.

    Return Values

    Returns true if needle is found in the array, false otherwise.

    Examples

    Example #1 in_array() example

    <?php
    $os     = array("Mac", "NT", "Irix", "Linux");
    if (    in_array("Irix", $os)) {
        echo     "Got Irix";
    }
    if (    in_array("mac", $os)) {
        echo     "Got mac";
    }
    ?>

    The second condition fails because in_array() is case-sensitive, so the program above will display: 

    Got Irix

    Example #2 in_array() with strict example

    <?php
    $a     = array('1.10', 12.4, 1.13);

    if (    in_array('12.4', $a, true)) {
        echo     "'12.4' found with strict check\n";
    }

    if (    in_array(1.13, $a, true)) {
        echo     "1.13 found with strict check\n";
    }
    ?>

    The above example will output:

    1.13 found with strict check

    Example #3 in_array() with an array as needle

    <?php
    $a     = array(array('p', 'h'), array('p', 'r'), 'o');

    if (    in_array(array('p', 'h'), $a)) {
        echo     "'ph' was found\n";
    }

    if (    in_array(array('f', 'i'), $a)) {
        echo     "'fi' was found\n";
    }

    if (    in_array('o', $a)) {
        echo     "'o' was found\n";
    }
    ?>

    The above example will output:

      'ph' was found
  'o' was found

    See Also

    • array_search() - Searches the array for a given value and returns the first corresponding key if successful
    • isset() - Determine if a variable is declared and is different than null
    • array_key_exists() - Checks if the given key or index exists in the array

    ＋add a note

    User Contributed Notes 3 notes

    up
    378
    beingmrkenny at gmail dot com
    10 years ago
    Loose checking returns some crazy, counter-intuitive results when used with certain arrays. It is completely correct behaviour, due to PHP's leniency on variable types, but in "real-life" is almost useless.

    The solution is to use the strict checking option.

    <?php

    // Example array

    $array = array(
            'egg' => true,
            'cheese' => false,
            'hair' => 765,
            'goblins' => null,
            'ogres' => 'no ogres allowed in this array'
    );

    // Loose checking -- return values are in comments

    // First three make sense, last four do not

    in_array(null, $array); // true
    in_array(false, $array); // true
    in_array(765, $array); // true
    in_array(763, $array); // true
    in_array('egg', $array); // true
    in_array('hhh', $array); // true
    in_array(array(), $array); // true

    // Strict checking

    in_array(null, $array, true); // true
    in_array(false, $array, true); // true
    in_array(765, $array, true); // true
    in_array(763, $array, true); // false
    in_array('egg', $array, true); // false
    in_array('hhh', $array, true); // false
    in_array(array(), $array, true); // false

    ?>
    up
    4
    rhill at xenu-directory dot net
    13 years ago
    I found out that in_array will *not* find an associative array within a haystack of associative arrays in strict mode if the keys were not generated in the *same order*:

    <?php

    $needle     = array(
            'fruit'=>'banana', 'vegetable'=>'carrot'
            );

    $haystack = array(
        array(    'vegetable'=>'carrot', 'fruit'=>'banana'),
        array(    'fruit'=>'apple', 'vegetable'=>'celery')
        );

    echo     in_array($needle, $haystack, true) ? 'true' : 'false';
    // Output is 'false'

    echo in_array($needle, $haystack) ? 'true' : 'false';
    // Output is 'true'

    ?>

    I had wrongly assumed the order of the items in an associative array were irrelevant, regardless of whether 'strict' is TRUE or FALSE: The order is irrelevant *only* if not in strict mode.
    up
    1
    thomas dot sahlin at gmail dot com
    12 years ago
    If you're creating an array yourself and then using in_array to search it, consider setting the keys of the array and using isset instead since it's much faster.

    <?php

    $slow     = array('apple', 'banana', 'orange');

    if (    in_array('banana', $slow))
        print(    'Found it!');

    $fast = array('apple' => 'apple', 'banana' => 'banana', 'orange' => 'orange');

    if (isset(    $fast['banana']))
        print(    'Found it!');

    ?>
    ＋add a note
    To Top