2015 Northeast PHP Conference

Dealing with Forms

One of the most powerful features of PHP is the way it handles HTML forms. The basic concept that is important to understand is that any form element will automatically be available to your PHP scripts. Please read the manual section on Variables from external sources for more information and examples on using forms with PHP. Here is an example HTML form:

Example #1 A simple HTML form

<form action="action.php" method="post">
 <p>Your name: <input type="text" name="name" /></p>
 <p>Your age: <input type="text" name="age" /></p>
 <p><input type="submit" /></p>

There is nothing special about this form. It is a straight HTML form with no special tags of any kind. When the user fills in this form and hits the submit button, the action.php page is called. In this file you would write something like this:

Example #2 Printing data from our form

Hi <?php echo htmlspecialchars($_POST['name']); ?>.
You are <?php echo (int)$_POST['age']; ?> years old.

A sample output of this script may be:

Hi Joe. You are 22 years old.

Apart from the htmlspecialchars() and (int) parts, it should be obvious what this does. htmlspecialchars() makes sure any characters that are special in html are properly encoded so people can't inject HTML tags or Javascript into your page. For the age field, since we know it is a number, we can just convert it to an integer which will automatically get rid of any stray characters. You can also have PHP do this for you automatically by using the filter extension. The $_POST['name'] and $_POST['age'] variables are automatically set for you by PHP. Earlier we used the $_SERVER superglobal; above we just introduced the $_POST superglobal which contains all POST data. Notice how the method of our form is POST. If we used the method GET then our form information would live in the $_GET superglobal instead. You may also use the $_REQUEST superglobal, if you do not care about the source of your request data. It contains the merged information of GET, POST and COOKIE data.

You can also deal with XForms input in PHP, although you will find yourself comfortable with the well supported HTML forms for quite some time. While working with XForms is not for beginners, you might be interested in them. We also have a short introduction to handling data received from XForms in our features section.

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User Contributed Notes 9 notes

sethg at ropine dot com
11 years ago
According to the HTTP specification, you should use the POST method when you're using the form to change the state of something on the server end. For example, if a page has a form to allow users to add their own comments, like this page here, the form should use POST. If you click "Reload" or "Refresh" on a page that you reached through a POST, it's almost always an error -- you shouldn't be posting the same comment twice -- which is why these pages aren't bookmarked or cached.

You should use the GET method when your form is, well, getting something off the server and not actually changing anything.  For example, the form for a search engine should use GET, since searching a Web site should not be changing anything that the client might care about, and bookmarking or caching the results of a search-engine query is just as useful as bookmarking or caching a static HTML page.
wojciech dot fornal at gmail dot com
4 months ago
@sethg at ropine dot com

You're partially right. For many people, the difference between POST/GET is about whether data is sent as a URL query (GET) or as a HTTP request payload together with headers (POST) and in most cases it is used so with regards to that.

In case of forms the difference between GET and POST has more to do with convenience and the fact that both methods fit to certain use cases and not with the fact whether a some resource is created/changed on the server or not (eg. login forms use POST method mainly to not expose sensitive data in URL etc.). It all depends on the back-end implementation what really happens after GET or POST request is received.

GET is good if you want the request to be cacheable and/or bookmarkable. In most HTML form cases though, POST seems always better, especially when we deal with long data (eg. forum post).

To be strict about HTTP verbs, POST verb usually means creation of new resource while to update an existing resource, the PUT method is used (not applicable in case of HTML forms except some additional hidden "method" form fields).

Those who are not familiar with HTTP verbs shall dive into HTTP specs (RFC 2616, section "9 Method Definitions")  and read a bit about REST.
Johann Gomes (johanngomes at gmail dot com)
4 years ago
Also, don't ever use GET method in a form that capture passwords and other things that are meant to be hidden.
3 years ago
Just a reminder about security: the chosen HTTP request verb (e.g. POST, GET) does not necessarily make the request "secure". Any information that is not transmitted over an encrypted channel (using SSL, i.e. HTTPS) is transmitted in plan text.

For secure transport of sensitive/private information over HTTP consider using SSL as this prevents eve's dropping of the information transmitted over HTTP.

[Edited by googleguy@php.net for clarity]
mail at pheunix dot in
6 months ago
It's true, comments do not take up PROCESSING time, but they do take some PARSING time in case you are not using a compile cache of some kind.
mail at pheunix dot in
18 days ago
I have loved having for my website and also my amazing provider.! So much better and faster.
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jerry4u at foxmail dot com
11 months ago
the difference of method GET and POST is really important.
mail at pheunix dot in
18 days ago
Thanks guys for sharing information about 12 Free And Open Source PHP Forum Scripts.
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behnam jaza faza
1 year ago
The note above says:

"Also see the import_request_variables() function. "

But dont:

This function has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 5.4.0.
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