PHP Form Handling

The PHP superglobals $_GET and $_POST are used to collect form-data.
The example below displays a simple HTML form with two input fields and a submit button:
When the user fills out the form above and clicks the submit button, the form data is sent 
for processing to a PHP file named "welcome.php". The form data is sent with 
the HTTP POST method.
To display the submitted data you could simply echo all the variables. The "welcome.php" looks like this:
The output could be something like this:
The same result could also be achieved using the HTTP GET method:
and "welcome_get.php" looks like this:
The code above is quite simple. However, the most important thing is missing. You need 
to validate form data to protect your script from malicious code.
Think SECURITY when processing PHP forms!
This page does not contain any form validation, it just shows how you can 
send and retrieve form data.
However, the next pages will show how to process PHP forms with security in mind! Proper validation of form data is important 
to protect your form from hackers and spammers!
Both GET and POST create an array (e.g. array( key1 => value1, 
key2 => value2, key3 => value3, ...)). This array holds key/value pairs, where 
keys are the names of the form controls and values are the input data from the user.
Both GET and POST are treated as $_GET and $_POST. These are superglobals, 
which means that they are always accessible, regardless of scope - and you can access them from any function,
class or file without having to do anything special.
$_GET is an array of variables passed to the current script via the URL parameters.
$_POST is an array of variables passed to the current script via the HTTP POST method.
Information sent from a form with the GET method is visible to everyone (all 
variable names and values are displayed in the URL). GET also has limits on the amount of 
information to send. The limitation is about 2000 characters. However, 
because the variables are displayed in the URL, it is possible to bookmark the 
page. This can be useful in some cases.
GET may be used for sending non-sensitive data.
Note: GET should NEVER be used for sending passwords or other sensitive information!
Information sent from a form with the POST method is invisible to others 
(all names/values are embedded within the body of the HTTP request) and 
has no limits on the amount of information to send.
Moreover POST supports advanced functionality such as support for multi-part 
binary input while uploading files to server.
However, because the variables are not displayed in the URL, it is not possible to bookmark the page.
Developers prefer POST for sending form data.
Next, lets see how we can process PHP forms the secure way!
If the form in the white section below gets submitted, how can you, in welcome.php, output the value from the "first name" field?
<form action="welcome.php" method="get">
First name: <input type="text" name="fname">
</form>

<html>
<body>
Welcome <?php echo ; ?>
</body>
</html>

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