(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
Parameters
needleThe searched value.
haystackNote:
If needle is a string, the comparison is done in a case-sensitive manner.
The array.
strictIf 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:
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', $a)) {echo "'o' was found\n";
}
?>
The above example will output:
'ph' was found 'o' was found
See Also
- array_search() - Searches the array for a given value and returns the first corresponding key if successful
- isset() - Determine if a variable is declared and is different than null
- array_key_exists() - Checks if the given key or index exists in the array
beingmrkenny at gmail dot com ¶
10 years ago
Loose checking returns some crazy, counter-intuitive results when used with certain arrays. It is completely correct behaviour, due to PHP's leniency on variable types, but in "real-life" is almost useless.
The solution is to use the strict checking option.
<?php// Example array$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); // truein_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); // truein_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?>
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.
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!');?>