Create a function that converts string to lowercase

/* There is a function in php wich convert all paragraph or 
string to lowercase*/
<?php
echo strtolower("Hey Samy, HAVE YOU CHECK THE LATEST MOVIE.");


// Output: hey samy, have you check the latest movie.
?>
/* The strtolower() function converts a string to lowercase.
Convert all characters to lowercase.*/
<?php
echo strtolower("Hello WORLD.");
?>
// Output: hello world.