php constant and define

php define and constant
define(name, value, case-insensitive)
if we not given third value, it wil take it as case sensitive (false)
case sensitive means there is a difference between capital and small
<?php
define("MESSAGE","Hello JavaTpoint PHP");
echo MESSAGE;
?>
prints
Hello JavaTpoint
echo message;	no data
<?php
define("MESSAGE","Hello JavaTpoint PHP,true");
echo MESSAGE;
?>
echo MESSAGE;	Hello JavaTpoint PHP
echo message;	Hello JavaTpoint PHP
<?php
const MESSAGE="Hello const by JavaTpoint PHP";
echo MESSAGE;
?>
echo MESSAGE;	Hello JavaTpoint PHP
echo message;	message
<?php
define("MSG", "JavaTpoint");
echo MSG, "</br>";	JavaTpoint
echo constant("MSG");	JavaTpoint
//both are similar
?>
echo constant("msg");	no output
same variable we can define number of times, but constant cannot redefined, once defined its over, that ist time value only displays if we define using constant