It is perfectly valid to use a built-in PHP keyword as a constant name - as long as you the constant() function to retrieve it later:
<?php
define('echo', 'My constant value');
echo constant('echo'); // outputs 'My constant value'
?>
It is perfectly valid to use a built-in PHP keyword as a constant name - as long as you the constant() function to retrieve it later:
<?php
define('echo', 'My constant value');
echo constant('echo'); // outputs 'My constant value'
?>