The $_POST variable is used to collect values from a form with method="post".

Why use $_POST?

Variables sent with HTTP POST are not shown in the URL.

Variables have no length limit.

However, because the variables are not displayed in the URL, it is not possible to bookmark the page.

 The $_POST Variable

The $_POST variable is an array of variable names and values sent by the HTTP POST method.

The $_POST variable is used to collect values from a form with method="post". Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

Example

<form action="welcome.php" method="post">
Enter your name: <input type="text" name="name" />
Enter your age: <input type="text" name="age" />
<input type="submit" />
</form>

When the user clicks the "Submit" button, the URL will not contain any form data, and will look something like this:

http://www.w3schools.com/welcome.php

The "welcome.php" file can now use the $_POST variable to catch the form data
(notice that the names of the form fields will automatically be the ID keys in the $_POST array): 

Welcome <?php echo $_POST["name"]; ?>.<br />

You are <?php echo $_POST["age"]; ?> years old!

The $_REQUEST Variable

The PHP $_REQUEST variable contains the contents of both $_GET, $_POST, and $_COOKIE.

The PHP $_REQUEST variable can be used to get the result from form data sent with both the GET and POST methods.

Example

Welcome <?php echo $_REQUEST["name"]; ?>.<br />
You are <?php echo $_REQUEST["age"]; ?> years old!

 Credit: www.w3schools.com

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