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".

Example 1

<?php
$a=array("a"=>"Horse","b"=>"Cat","c"=>"Dog");
print_r(array_keys($a));
?>

The output of the code above will be:

Array ( [0] => a [1] => b [2] => c )

Example 2

Using the value parameter.

<?php
$a=array("a"=>"Horse","b"=>"Cat","c"=>"Dog");
print_r(array_keys($a,"Dog"));
?>

The output of the code above will be:

Array ( [0] => c)

Using the strict parameter: false

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

The output of the code above will be:

Array ( [0] => 0 [1] => 3 )

Using the strict parameter: true

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

The output of the code above will be:

Array ( [0] => 3)

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