Hướng dẫn dùng w3schools form trong PHP

The PHP superglobals $_GET and $_POST are used to collect form-data.

Nội dung chính

• PHP – A Simple HTML Form
• GET vs. POST
• When to use GET?
• When to use POST?
• PHP Exercises
• Test Yourself With Exercises
• PHP – Keep The Values in The Form
• PHP – Complete Form Example

PHP – A Simple HTML Form

• PHP – A Simple HTML Form
  • Example
  • Example
• GET vs. POST
• When to use GET?
• When to use POST?
• PHP Exercises
• Test Yourself With Exercises
• Exercise:
• PHP – Keep The Values in The Form
• PHP – Complete Form Example

The example below displays a simple HTML form with two input fields and a submit button:

Example

Run Example »

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:

Welcome

Your email address is:

The output could be something like this:

Welcome John
Your email address is

The same result could also be achieved using the HTTP GET method:

Example

Run Example »

and “welcome_get.php” looks like this:

Welcome

Your email address
is:

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!

GET vs. POST

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.

When to use GET?

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!

When to use POST?

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!

PHP Exercises

Test Yourself With Exercises

Exercise:

If the form in the white section below gets submitted, how can you, in welcome.php, output the value from the “first name” field?

First name: 




Welcome 

This chapter shows how to keep the values in the input fields when the user hits the submit button.

PHP – Keep The Values in The Form

To show the values in the input fields after the user hits the submit button, we add a little PHP script inside the value attribute of the following input fields: name, email, and website. In the comment textarea field, we put the script between the and tags. The little script outputs the
value of the $name, $email, $website, and $comment variables. 

Then, we also need to show which radio button that was checked. For this, we must manipulate the checked attribute (not the value attribute for radio buttons):

Name: ”>

E-mail: ”>

Website: ”>

Comment: <?php echo $comment;?>

Gender:

value=”female”>Female

value=”male”>Male
$gender==”other”) echo “checked”;?>
value=”other”>Other

PHP – Complete Form Example

Here is the complete code for the PHP Form Validation Example: