ajax - mysql database

We already know how to run an external PHP script with AJAX, so let's take it to the next level and pull some data down from a MySQL database. Our "order.html" file and PHP script will have to be updated and we also need to make a new database.

create the mysql table

To clearly illustrate how easy it is to access information from a database using Ajax, we are going to build MySQL queries on the fly and display the results on "order.html".

Create a new database or use an existing one and then import the tableajax_example.sql to that database. This sql file will create the table ajax_exampleand insert all the data rows. The table has four columns:

ae_name - The name of the person
ae_age - Person's age
ae_sex - The gender of the person
ae_wpm - The words per minute that person can type

update order.html

We want to be able to build queries from our HTML file, so there are a few form elements that will need to be added. The three inputs we are going to implement are:

Maximum Age (Text Input) - Let the user select the maximum age to be returned.
Maximum WPM (Text Input) - Let the user select the maximum wpm to returned.
Gender (Select Input) - Let the user select the gender of a valid person.

order.html HTML/Javascript Code:

<html>
<body>

<script language="javascript" type="text/javascript">
<!-- 
//Browser Support Code
function ajaxFunction(){
 var ajaxRequest;  // The variable that makes Ajax possible!
 
 try{
  // Opera 8.0+, Firefox, Safari
  ajaxRequest = new XMLHttpRequest();
 } catch (e){
  // Internet Explorer Browsers
  try{
   ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (e) {
   try{
    ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
   } catch (e){
    // Something went wrong
    alert("Your browser broke!");
    return false;
   }
  }
 }
 // Create a function that will receive data sent from the server
 ajaxRequest.onreadystatechange = function(){
  if(ajaxRequest.readyState == 4){
   document.myForm.time.value = ajaxRequest.responseText;
  }
 }
 var age = document.getElementById('age').value;
 var wpm = document.getElementById('wpm').value;
 var sex = document.getElementById('sex').value;
 var queryString = "?age=" + age + "&wpm=" + wpm + "&sex=" + sex;
 ajaxRequest.open("GET", "ajax-example.php" + queryString, true);
 ajaxRequest.send(null); 
}

//-->
</script>



<form name='myForm'>
Max Age: <input type='text' id='age' /> <br />
Max WPM: <input type='text' id='wpm' />
<br />
Sex: <select id='sex'>
<option>m</option>
<option>f</option>
</select>
<input type='button' onclick='ajaxFunction()' value='Query MySQL' />
</form>
</body>
</html>

If the new Javascript code is foreign to you, be sure to check out our lesson onJavascript's getElementById Function.

With our new Javascript code
var queryString = "?age=" + age + "&wpm=" + wpm + "&sex=" + sex;
we have built a query string to pass along the information from our HTML form to our PHP script.

ajax - passing variables via query string

A query string is a way of passing information by appending data onto the URL. You may have often seen it on the web, it's all the information that appears after a question mark "?". When you submit a form using GET it builds a query string, all we're doing here is manually building our own.

http://www.tizag.com/somescript.php?variable1=value1&variable2=value2

The left side of the equals operator is the variable name and the right side is the variable's value. Also, each variable is separated with an ampersand &.

For example, if we wanted to send the variables age, sex, and wpm with values 20, f, 40 to our PHP script ajax-example.php then our URL would look like:

http://www.tizag.com/ajax-example.php?age=20&sex=f&wpm=40

Now we need to build a new PHP script to take these variables and run a MySQL query for us.

ajax - create ajax-example.php script

We already changed the destination URL in our ajaxRequest.open method, now we need to make a script to grab those variables from the query string and execute a MySQL Query. We're also going to use a special functionmysql_real_escape_string to prevent any harmful user input from doing something they aren't supposed to (we're going to take steps against SQL Injection).

ajax-example.php Code:

<?php
$dbhost = "localhost";
$dbuser = "dbusername";
$dbpass = "dbpassword";
$dbname = "dbname";
 //Connect to MySQL Server
mysql_connect($dbhost, $dbuser, $dbpass);
 //Select Database
mysql_select_db($dbname) or die(mysql_error());
 // Retrieve data from Query String
$age = $_GET['age'];
$sex = $_GET['sex'];
$wpm = $_GET['wpm'];
 // Escape User Input to help prevent SQL Injection
$age = mysql_real_escape_string($age);
$sex = mysql_real_escape_string($sex);
$wpm = mysql_real_escape_string($wpm);
 //build query
$query = "SELECT * FROM ajax_example WHERE ae_sex = '$sex'";
if(is_numeric($age))
 $query .= " AND ae_age <= $age";
if(is_numeric($wpm))
 $query .= " AND ae_wpm <= $wpm";
 //Execute query
$qry_result = mysql_query($query) or die(mysql_error());

 //Build Result String
$display_string = "<table>";
$display_string .= "<tr>";
$display_string .= "<th>Name</th>";
$display_string .= "<th>Age</th>";
$display_string .= "<th>Sex</th>";
$display_string .= "<th>WPM</th>";
$display_string .= "</tr>";

 // Insert a new row in the table for each person returned
while($row = mysql_fetch_array($qry_result)){
 $display_string .= "<tr>";
 $display_string .= "<td>$row[ae_name]</td>";
 $display_string .= "<td>$row[ae_age]</td>";
 $display_string .= "<td>$row[ae_sex]</td>";
 $display_string .= "<td>$row[ae_wpm]</td>";
 $display_string .= "</tr>";
 
}
echo "Query: " . $query . "<br />";
$display_string .= "</table>";
echo $display_string;
?>

the next step - updating order.html

We have completed our initial order.html and ajax-example.php setup, now we just need our order.html page to update correctly when a query is returned. We'll be using a couple advanced Javascript functions to update a segment of order.html with the MySQL result display_string.

Ajax Tutorial Part 6