The syntax for defining constant is as below:
bool define ( string $name , mixed $value [, bool $case_insensitive = false ])
<?php define("hello", "Hi There."); echo hello; echo "<br>"; echo Hello; echo "<br>"; //To allow case insensitive, set the third parameter to be true. define("greeting", "How are you?", true); echo GREETING; echo "<br>"; echo Greeting; ?>
Note that there are 2 parts in the above code. The top part is case sensitive and the second part is case insensitive.
You can try to run the code here.