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<option value="1">Peter Griffin</option>
<option value="2">Lois Griffin</option>
<option value="3">Glenn Quagmire</option>
<option value="4">Joseph Swanson</option>
</select>
</form></pre>
<pre><p>
<div id="txtHint"><b>User info will be listed here.</b></div>
</p></pre>
<pre></body>
</html></pre>
</td>
</tr>
</table>
<h2>Example Explained - The HTML Form</h2>
<p>As you can see it is just a simple HTML form with a drop down box called
"users" with names and the "id" from the database as option values.</p>
<p>The paragraph below the form contains a div called "txtHint". The div is used
as a placeholder for info retrieved from the web server.</p>
<p>When the user selects data, a function called "showUser()" is executed.
The execution of the function is triggered by the "onchange" event.</p>
<p>In other
words: Each time the user changes the value in the drop down box, the function
showUser() is called.</p>
<hr>
<h2>The JavaScript</h2>
<p>This is the JavaScript code stored in the file "selectuser.js":</p>
<table class="ex" id="table7" border="1" width="100%">
<tr>
<td>
<pre>var xmlHttp</pre>
<pre>function showUser(str)
{
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request")
return
}
var url="getuser.php"
url=url+"?q="+str
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
}</pre>
<pre>function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText
}
}</pre>
<pre>function GetXmlHttpObject()
{
var xmlHttp=null;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
//Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlHttp;
}</pre>
</td>
</tr>
</table>
<h2>Example Explained</h2>
<p>The stateChanged() and GetXmlHttpObject functions are the same as in the
<a href="php_ajax_suggest.asp">PHP AJAX Suggest</a> chapter, you can go
to there for an explanation of those.</p>
<p><b>The showUser() Function</b></p>
<p>If an item in the drop down box is selected the function
executes the following:</p>
<ol>
<li>Calls on the GetXmlHttpObject function to create an XMLHTTP object</li>
<li>Defines the url (filename) to send to the server</li>
<li>Adds a parameter (q) to the url with the content of the dropdown box
</li>
<li>Adds a random number to prevent the server from using a cached file</li>
<li>Call stateChanged when a change is triggered</li>
<li>Opens the XMLHTTP object with the given url.</li>
<li>Sends an HTTP request to the server</li>
</ol><hr>
<h2>The PHP Page</h2>
<p>The server page called by the JavaScript, is a simple PHP file called
"getuser.php".</p>
<p>The page is written in PHP and uses a MySQL databse.</p>
<p>The code runs a SQL query against a database and returns the result as an HTML
table:</p>
<table class="ex" id="table8" border="1" width="100%">
<tr>
<td>
<pre><?php
$q=$_GET["q"];
$con = mysql_connect('localhost', 'peter', 'abc123');
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("ajax_demo", $con);
$sql="SELECT * FROM user WHERE id = '".$q."'";
$result = mysql_query($sql);
echo "<table border='1'>
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
<th>Hometown</th>
<th>Job</th>
</tr>";
while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>" . $row['FirstName'] . "</td>";
echo "<td>" . $row['LastName'] . "</td>";
echo "<td>" . $row['Age'] . "</td>";
echo "<td>" . $row['Hometown'] . "</td>";
echo "<td>" . $row['Job'] . "</td>";
echo "</tr>";
}
echo "</table>";
mysql_close($con);
?>
</pre>
</td>
</tr>
</table>
<h2>Example Explained</h2>
<p>When the query is sent from the JavaScript to the PHP page the following
happens:</p>
<ol>
<li>PHP opens a connection to a MySQL server</li>
<li>The "user" with the specified name is found</li>
<li>A table is created and the data is inserted and sent to the "txtHint"
placeholder</li>
</ol>
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