(PHP 4, PHP 5, PHP 7)
array_keys — Return all the keys or a subset of the keys of an array
array_keys ( array $array ) : array
array_keys ( array $array , mixed $search_value [, bool $strict = false ] ) : array
array_keys() returns the keys, numeric and string, from the array.
If a search_value is specified, then only the keys for that value are returned. Otherwise, all the keys from the array are returned.
array
An array containing keys to return.
search_value
If specified, then only keys containing these values are returned.
strict
Determines if strict comparison (===) should be used during the search.
Returns an array of all the keys in array.
Example #1 array_keys() example
<?php
$array = array(0 => 100, "color" => "red");
print_r(array_keys($array));
$array = array("blue", "red", "green", "blue", "blue");
print_r(array_keys($array, "blue"));
$array = array("color" => array("blue", "red", "green"),
"size" => array("small", "medium", "large"));
print_r(array_keys($array));
?> The above example will output:
Array
(
[0] => 0
[1] => color
)
Array
(
[0] => 0
[1] => 3
[2] => 4
)
Array
(
[0] => color
[1] => size
)
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https://www.php.net/manual/en/function.array-keys.php