Array Functions
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PHP array_keys() Function

Topic: PHP Array ReferencePrev|Next

Description

The array_keys() function return all the keys or a subset of the keys of an array.

The following table summarizes the technical details of this function.

Return Value: Returns an array containing the keys.
Version: PHP 4+

Syntax

The basic syntax of the array_keys() function is given with:

array_keys(array, value, strict);

The following example shows the array_keys() function in action.

<?php
// Sample array
$persons = array("Harry"=>18, "Clark"=>"32", "John"=>24, "Peter"=>32);
    
// Getting all the keys from the persons array
print_r(array_keys($persons));
?>

Parameters

The array_keys() function accepts the following parameters.

Parameter Description
array Required. Specifies the array to be used.
value Optional. If specified, then only keys containing these values are returned.
strict Optional. Determines if strict comparison (===) should be used during the value search. Possible values are true and false. Default value is false.

Note: In strict comparison (using strict equality === operator) value and data type must be equal, therefore in strict comparison integer 4 is not equal to string "4".


More Examples

Here're some more examples showing how array_keys() function actually works:

The following example return all the keys from the persons array containing the value 32.

<?php
// Sample array
$persons = array("Harry"=>18, "Clark"=>"32", "John"=>24, "Peter"=>32);
    
// Getting all the keys having value 32
print_r(array_keys($persons, 32));
?>

The following example will return only those key which has integer value 32 using strict comparison. This can be simply done by setting the strict parameter to true.

<?php
// Sample array
$persons = array("Harry"=>18, "Clark"=>"32", "John"=>24, "Peter"=>32);
    
// Getting all the keys having integer value 32
print_r(array_keys($persons, 32, true));
?>
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