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PHP array_change_key_case() Function

PHP array_change_key_case() Function is used to change case of all of the keys in a given array either to lower case or upper case. Numbered indices are left as is.

PHP array_change_key_case() function is an inbuilt function of PHP.

array_change_key_case – Changes the case of all keys in an array


array_change_key_case(array, case)

Parameter Values

arrayRequired. Specifies the array to use
Possible values: CASE_LOWER – Default value. Changes the keys to lowercase CASE_UPPER – Changes the keys to uppercase
PHP array_change_key_case() Function Parameter Values

 If the convert_case parameter is not passed then it’s default value is taken which is CASE_LOWER.

Return Value

Returns an array with its keys in lowercase or uppercase, or FALSE if array is not an array



// PHP code to illustrate array_change_key_case()
// Both the parameters are passed
function change_case($in_array){
	return(array_change_key_case($in_array, CASE_UPPER));

// Driver Code
$array = array("Anil" => 90, "RagHav" => 80,
			"Abdul" => 95, "Peter" => 85, "RISHAV" => 70);

Output of above example
    $vow=array("a"=>"a", "e"=>"e", "i"=>"i", "o"=>"o", "u"=>"u");  
    print_r(array_change_key_case($vow,CASE_UPPER));  //Array(  [A]=>a  [E]=>e  [I]=>i  [O]=>o  [U]=>u  )
    $sal=array("Rahul"=> "10000" , "Ajay"=> "15000" , "Sid"=> "20000" );  
    print_r(array_change_key_case( $sal, CASE_LOWER ) );  //Array ( [rahul]=> 10000  [ajay]=> 15000  [sid]=> 20000 )

If two or more array keys will be the same after running array_change_key_case( ) function, the latest array will override the other.

    $city=array("a"=> "Agra" , "B"=> "Bhopal" , "c"=> "Chennai" ,"b"=> "Bengaluru"  );  
    print_r(array_change_key_case( $city, CASE_UPPER ) );  //Array ( [A] => Agra [B] => Bengaluru [C] => Chennai )

If we ignore the second parameter in the function array_change_key_case( ) then the keys will be converted to lowercase.

    $age=array("RAHUL"=> "10" , "VIKAS"=> "20" , "SID"=> "25"  );  
    print_r(array_change_key_case( $age) );  //Array ([rahul]=> 10  [vikas]=> 20  [sid]=> 25 )