15500usd to php

/* strtolower() function converts  string to lowercase. */
<?php
echo strtolower("Hello WORLD 123");
?>
// Output:hello world 123strtolower ( string $string ) : string 
//Returns string with all alphabetic characters converted to lowercase.
$string = 'HELLO WORLD';
echo strtolower($string); //Output: 'hello world'
$string = 'HeLlO WoRlD';
echo strtolower($string); //Output: 'hello world'