Return all the keys or a subset of the keys of an array
Syntax
array_keys(array $array): array
array_keys(array $array, mixed $search_value, bool $strict = false): array
Parameters
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.
Return
Returns an array of all the keys in array.
Examples
1 · array · Indexed
<? $array = array(null, false, true, 0, 1); $return = array_keys($array); print_r($return); ?>
Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 )
2 · array · Associative
<? $array = array( "a" => null, "b" => false, "c" => true, "d" => 0, "e" => 1 ); $return = array_keys($array); print_r($return); ?>
Array ( [0] => a [1] => b [2] => c [3] => d [4] => e )
3 · search_value · Indexed
<? $array = array(null, false, true, 0, 1); $search_value = 1; $return = array_keys($array, $search_value); print_r($return); ?>
Array ( [0] => 2 [1] => 4 )
4 · search_value · Associative
<? $array = array( "a" => null, "b" => false, "c" => true, "d" => 0, "e" => 1 ); $search_value = 1; $return = array_keys($array, $search_value); print_r($return); ?>
Array ( [0] => c [1] => e )
5 · strict · Indexed
<? $array = array(null, false, true, 0, 1); $search_value = 1; $strict = true; $return = array_keys($array, $search_value, $strict); print_r($return); ?>
Array ( [0] => 4 )
6 · strict · Associative
<? $array = array( "a" => null, "b" => false, "c" => true, "d" => 0, "e" => 1 ); $search_value = 1; $strict = true; $return = array_keys($array, $search_value, $strict); print_r($return); ?>
Array ( [0] => e )