AJAX can be used for interactive communication with a database.

AJAX Database Example

The following example will demonstrate how a web page can fetch information from a database with AJAX:

Example

 

Person info will be listed here…

Example Explained – The MySQL Database

The database table we use in the example above looks like this:

id FirstName LastName Age Hometown Job
1 Peter Griffin 41 Quahog Brewery
2 Lois Griffin 40 Newport Piano Teacher
3 Joseph Swanson 39 Quahog Police Officer
4 Glenn Quagmire 41 Quahog Pilot

Example Explained

In the example above, when a user selects a person in the dropdown list above, a function called “showUser()” is executed.

The function is triggered by the onchange event.

Here is the HTML code:

Example

Person info will be listed here…

 



Code explanation:


First, check if person is selected. If no person is selected (str == “”), clear the content of txtHint and exit the function. If a person is selected, do the following:


    

  • Create an XMLHttpRequest object
    • 

  • Create the function to be executed when the server response is ready
    • 

  • Send the request off to a file on the server
    • 

  • Notice that a parameter (q) is added to the URL (with the content of the dropdown list)
    • 



The PHP File


The page on the server called by the JavaScript above is a PHP file called “getuser.php”.


The source code in “getuser.php” runs a query against a MySQL database, and returns the result in an HTML table:






 




Explanation: When the query is sent from the JavaScript to the PHP file, the following happens:


    

  1. PHP opens a connection to a MySQL server
    2. 

  2. The correct person is found
    3. 

  3. An HTML table is created, filled with data, and sent back to the “txtHint” placeholder
    4.