PHP array_keys() Function

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# PHP array_keys() Function

Complete PHP Array Reference

## Definition and Usage

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

## Syntax

    array_keys(array,value)

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)

## Example 3

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 )

## Example 4

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)

Complete PHP Array Reference

From http://www.w3schools.com (Copyright Refsnes Data)