How to convert string to lowercase in PHP?

Use strtolower($string). Example: strtolower('HELLO') returns 'hello'.

Does strtolower() work with UTF-8?

strtolower() only works with ASCII. For UTF-8, use mb_strtolower($str, 'UTF-8').

String Function PHP 4+

The strtolower() function converts all alphabetic characters in a string to lowercase.

strtolower(string $string): string

Parameter	Type	Description
`$string`	string	The input string

Returns the string with all alphabetic characters converted to lowercase.

Output

Click Run to execute your code

<?php
$input = "YES";
if (strtolower($input) === "yes") {
    echo "User agreed!";
}
?>

<?php
$email = "[email protected]";
$normalized = strtolower($email);
echo $normalized;  // "[email protected]"
?>

Note: For UTF-8 strings with special characters, use mb_strtolower() instead.