PHP array_keys() Function

Return an array containing the keys:

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5","Toyota"=>"Highlander");
print_r(array_keys($a));
?>

Definition and Usage

The array_keys() function returns an array containing the keys.

array_keys( array, value, strict)

Parameter	Description
array	Required. Specifies an array
value	Optional. You can specify a value, then only the keys with this value are returned
strict	Optional. Used with the value parameter. Possible values: true - Returns the keys with the specified value, depending on type: the number 5 is not the same as the string "5". false - Default value. Not depending on type, the number 5 is the same as the string "5".

Return Value:	Returns an array containing the keys
PHP Version:	4+
Changelog:	The strict parameter was added in PHP 5.0

Using the value parameter:

<?php
$a=array("Volvo"=>"XC90","BMW"=>"X5","Toyota"=>"Highlander");
print_r(array_keys($a,"Highlander"));
?>

Using the strict parameter, false:

<?php
$a=array(10,20,30,"10");
print_r(array_keys($a,"10",false));
?>

Using the strict parameter, true:

<?php
$a=array(10,20,30,"10");
print_r(array_keys($a,"10",true));
?>