Detailed explanation of array_keys() function in php

The array_keys() function returns an array containing all keys found in the searched array. Its form is as follows:

array array_keys(array array[,mixed search_value])

If the optional parameter search_value is included, only keys matching the value will be returned. The following example will output all arrays found in the $fruit array:

$fruits["apple"] = "red";  
$fruits["banana"] = "yellow";  
$fruits["watermelon"]="green";  
$keys = array_keys($fruits);  
print_r($keys);  
  
//Array ( [0] => apple [1] => banana [2] => watermelon )

Returns a new array containing all the key names in the array:

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

Definition and Usage

array_keys () function returns a new array containing all the keys in the array.

Syntax

array_keys(array,value,strict)

array Required. Specifies an array.

value Optional. You can specify a key value, and then only the key name corresponding to that key value will be returned.

strict Optional. Used with the value parameter. Possible values:

true - Returns the key name with the specified key value. Depending on the type, the number 5 is not the same as the string "5".

false - the default value. Independent of type, the number 5 is the same as the string "5".

Return value:

Returns a new array containing all the key names in the array.

Parameters:

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

Use strict parameter (false):

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

Use strict parameter (true):

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