in_array

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

    in_array — 检查数组中是否存在某个值

    说明

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

    大海捞针，在大海（haystack）中搜索针（ needle），如果没有设置 strict 则使用宽松的比较。

    参数

    needle

    待搜索的值。

    注意:

    如果 needle 是字符串，则比较是区分大小写的。

    haystack

    待搜索的数组。

    strict

    如果第三个参数 strict 的值为 true 则 in_array() 函数还会检查 needle 的类型是否和 haystack 中的相同。

    注意:

    在 PHP 8.0.0 之前，string needle 在非严格模式下将会匹配数组中的值 0，反之亦然。这可能会导致不希望的结果。其它类型也存在类似的边缘情况。如果不是绝对确定有关值的类型，请始终使用 strict flag 以避免意外行为。

    返回值

    如果找到 needle 则返回 true，否则返回 false。

    示例

    示例 #1 in_array() 例子

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

    第二个条件失败，因为 in_array() 是区分大小写的，所以以上程序显示为： 

    Got Irix

    示例 #2 in_array() 严格类型检查例子

    <?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";
    }
    ?>

    以上示例会输出：

    1.13 found with strict check

    示例 #3 in_array() 中用数组作为 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";
    }
    ?>

    以上示例会输出：

    'ph' was found
  'o' was found

    参见

    • array_search() - 在数组中搜索给定的值，如果成功则返回首个相应的键名
    • isset() - 检测变量是否已声明并且其值不为 null
    • array_key_exists() - 检查数组里是否有指定的键名或索引

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    用户贡献的备注 5 notes

    up
    411
    beingmrkenny at gmail dot com
    13 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
    3
    Julian Sawicki
    1 year ago
    Here is a recursive in_array function:

    <?php

    $myNumbers     = [
    [    1,2,3,4,5],
    [    6,7,8,9,10],
    ];

    $array = [
    'numbers' => $myNumbers
    ];

    // Let's try to find number 7 within $array
    $hasNumber = in_array(7, $array, true); // bool(false)
    $hasNumber = in_array_recursive(7, $array, true); // bool(true)

    function in_array_recursive(mixed $needle, array $haystack, bool $strict): bool
    {
    foreach (    $haystack as $element) {
    if (    $element === $needle) {
    return     true;
    }

    $isFound = false;
    if (    is_array($element)) {
    $isFound = in_array_recursive($needle, $element, $strict);
    }

    if (    $isFound === true) {
    return     true;
    }
    }

    return     false;
    }
    up
    10
    rhill at xenu-directory dot net
    15 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
    leonhard dot radonic+phpnet at gmail dot com
    2 years ago
    I got an unexpected behavior working with in_array. I'm using following code:

    <?php
    // ...
    $someId = getSomeId(); // it gets generated/fetched by another service, so I don't know what value it will have. P.S.: it's an integer

    // The actual data in my edge-case scenario:
    // $someId = 0;
    // $anyArray = ['dataOne', 'dataTwo'];
    if (in_array($someId, $anyArray)) {
    // do some work
    }
    // ...
    ?>

    With PHP7.4, in_array returns boolean true.
    With PHP8.1, in_array returns boolean false.

    It took me quite some time to find out what's going on.
    up
    -4
    Armands Rieksti
    1 year ago
    I'd like to point out that, if you're using Enum data structures and want to compare whether an array of strings has a certain string Enum in it, you need to cast it to a string.

    From what I've tested, the function works correctly:
    if the array is filled with strings and you're searching for a string;
    if the array is filled with Enums and you're searching for an Enum.
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