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AJAX and MySQL IN PHP

by MH RISHAD - 07 Apr 2019
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AJAX can be used for interactive communication with a database.

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
 

 

 

 

 





  Select a person:
  Peter Griffin
  Lois Griffin
  Joseph Swanson
  Glenn Quagmire
  

 

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:

 

 

 

 

 

 

 


$q = intval($_GET['q']);

$con = mysqli_connect('localhost','peter','abc123','my_db');
if (!$con) {
    die('Could not connect: ' . mysqli_error($con));
}

mysqli_select_db($con,"ajax_demo");
$sql="SELECT * FROM user WHERE id = '".$q."'";
$result = mysqli_query($con,$sql);

echo "






";
while($row = mysqli_fetch_array($result)) {
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
}
echo "

Firstname Lastname Age Hometown Job
" . $row['FirstName'] . " " . $row['LastName'] . " " . $row['Age'] . " " . $row['Hometown'] . " " . $row['Job'] . "

";
mysqli_close($con);
?>
 

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. The correct person is found
  3. An HTML table is created, filled with data, and sent back to the "txtHint" placeholder
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