Tham khảo tài liệu 'tự học html và css trong 1 giờ - part 67', công nghệ thông tin, đồ họa - thiết kế - flash phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 636 LESSON 21 Taking Advantage of the Server function alsoAdd a 0 b 0 return add a b Processing Forms You learned how to create forms back in Lesson 11 Designing Forms and although I explained how to design a form I didn t give you a whole lot of information about what to do with form data once it s submitted. Now I explain how PHP makes data that has been submitted available to your PHP scripts. When a user submits a form PHP automatically decodes the variables and copies the values into some built-in variables. Built-in variables are like built-in functions you can always count on their being defined when you run a script. The three associated with form data are _GET _POST and _REQUEST. These variables are all associative arrays and the names assigned to the form fields on your form are the keys to the arrays. _GET contains all the parameters submitted using the GET method in other words in the query string portion of the URL . The _POST method contains all the parameters submitted via POST in the response body. _REQUEST contains all the form parameters regardless of how they were submitted. Unless you have a specific reason to differentiate between GET and POST you can use _REQUEST. Let s look at a simple example of a form form action method post Enter your name input type text name yourname br input type submit form When the user submits the form the value of the yourname field will be available in _POST and _REQUEST. You could return it to the user like this p Hello _REQUEST yourname . Thanks for visiting. p Preventing Cross-Site Scripting You have to be careful when you display data entered by a user on a web page because malicious users can include HTML tags and JavaScript in their input in an attempt to trick other users who might view that information into doing something they might not want to do such as entering their password to your site and submitting it to another site. This is known as a cross-site scripting attack. To prevent malicious .
