Send and get Query String

PHP, like CGI, ASP, and JSP, can send and retrieve data by using a form or a link. For example, if you have a form that has an input field such as this:

<INPUT TYPE=TEXT NAME="userName">

Given you enter a value "John" and submit it. Then the variable "userName" has a value of "John".

Then you can access it in the same page or in the next page:

echo "Hi " . $_POST['userName'];

If you use a link like:

<a href="nextpage.php?userName=John">John</a>

Then you can retrieve the value:

echo "Hi " . $_GET['userName'];

There are some functions for passing message. For example, if you transform a message that contains HTML code and you want to keep the HTML code not interpreted, you can use the htmlentities() function:

$message = htmlentities($message);

The below are some useful functions