(PCC)[PHP] Keywords classes functions and user defined functions ARE NOT case sensitive in php

(PCC)::[Keywords-classes-functions-and-user-defined-functions-ARE-NOT-case-sensitive-in-php]::[php]

<!DOCTYPE html>
<html>
<body>

<?php
ECHO "Hello World!<br>";
echo "Hello World!<br>";
EcHo "Hello World!<br>";
?> 

</body>
</html>

"; echo "Hello World!
"; EcHo "Hello World!
"; ?>