PHP Tutorial - PHP array_keys() function

Definition

The array_keys() function returns an array of all the keys in that array.

Syntax

PHP array_keys() function has the following syntax

array array_keys ( array arr [, mixed value [, bool strict]] )

Parameter

Parameter	Is Required	Description
arr	Required.	Array to search
value	Optional.	Only the keys with this value are returned
strict	Optional.	Used with the value parameter.

Possible values for strict:

Value	Description
true	Check type. the number 9 is not the same as the string "9".
false	Default value. Not checking type, the number 9 is the same as the string "9".

By default, this is done by checking each key's value with the == operator (is equal to); however, if you specify 1 as the third parameter, the check will be done with === (identical to).

Example

Get all keys in an array


<?php
    $users[0] = 'PHP';
    $users[1] = 'Java';
    $users[2] = 'java2s.com';
    $userids = array_keys($users);
    print_r($userids);
?>

The code above generates the following result.

Example 2

Using the value parameter:


<?php
    $a=array("p"=>"PHP","j"=>"java2s.com","a"=>"Apple");
    print_r(array_keys($a,"java2s.com"));
?>

The code above generates the following result.

Example 3

Using the strict parameter, false:


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

The code above generates the following result.

Example 4

Using the strict parameter, true:


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

The code above generates the following result.