In this tutorial, you will be learning about the $_REQUEST[] variable.
$_REQUEST is a PHP superglobal variable that lets you access data that's been sent to the page from another page.
The difference with $_POST[] is that $_REQUEST[] can access data sent via either the POST or the GET method, while $_POST[] or $_GET[] can only access data sent via their own method type.
So to illustrate this, let's have a look at the example below.
Example
a.php
<html>
<head><title></title></head>
<body>
<form action='a.php' method='POST'>
<input type='text' name='a'>
<br>
<input type='submit' value='submit'>
</body>
</html>
b.php
<?php
echo $_REQUEST['a'];
?>
Result
<?php
echo $_POST["a"];
?>
The above code would have yield the same results as if you used $_REQUEST['a']. However, the code below will not work.
<?php
echo $_GET["a"];
?>
You cannot access POST data using the $_GET[] variable.