PHP and AJAX Suggest
AJAX Suggest
In the AJAX example below we will demonstrate how a web page can communicate
with a web server online as a user enters data into a web form.
Type a Name in the Box Below
Suggestions:
This example consists of three pages:
- a simple HTML form
- a JavaScript
- a PHP page
The HTML Form
This is the HTML page. It contains a simple HTML form and a link to a
JavaScript:
<html>
<head>
<script src="clienthint.js"></script>
</head>
<body>
<form>
First Name:
<input type="text" id="txt1"
onkeyup="showHint(this.value)">
</form>
<p>Suggestions: <span id="txtHint"></span></p>
</body>
</html>
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Example Explained - The HTML Form
As you can see, the HTML page above contains a simple HTML form with an input field called
"txt1".
The form works like this:
- An event is triggered when the user presses, and releases a key in the
input field
- When the event is triggered, a function called showHint() is executed.
- Below the form is a <span> called "txtHint". This is used as a placeholder for
the return data of the showHint() function.
The JavaScript
The JavaScript code is stored in "clienthint.js" and linked to the HTML
document:
var xmlHttp;
function showHint(str)
{
if (str.length==0)
{
document.getElementById("txtHint").innerHTML="";
return;
}
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request");
return;
}
var url="gethint.php";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}
function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText;
}
}
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;
}
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Example Explained
The showHint() Function
This function executes every time a character is entered in the input field.
If there is some input in the text field (str.length > 0) the function
executes the following:
- Defines the url (filename) to send to the server
- Adds a parameter (q) to the url with the content of the input field
- Adds a random number to prevent the server from using a cached file
- Calls on the GetXmlHttpObject function to create an XMLHTTP object, and tells the object to execute a function
called stateChanged when a change is triggered
- Opens the XMLHTTP object with the given url.
- Sends an HTTP request to the server
If the input field is empty, the function simply clears the content of the
txtHint placeholder.
The stateChanged() Function
This function executes every time the state of the XMLHTTP
object changes.
When the state changes to 4 (or to "complete"), the content of the txtHint
placeholder is filled with the response text.
The GetXmlHttpObject() Function
AJAX applications can only run in web browsers with complete XML support.
The code above called a function called GetXmlHttpObject().
The purpose of the function is to solve the problem of creating different
XMLHTTP objects for different browsers.
This is explained in the previous chapter.
The PHP Page
The server page called by the JavaScript code is a simple PHP file called "gethint.php".
The code in the "gethint.php" checks an array of names and returns the
corresponding names to the client:
<?php
// Fill up array with names
$a[]="Anna";
$a[]="Brittany";
$a[]="Cinderella";
$a[]="Diana";
$a[]="Eva";
$a[]="Fiona";
$a[]="Gunda";
$a[]="Hege";
$a[]="Inga";
$a[]="Johanna";
$a[]="Kitty";
$a[]="Linda";
$a[]="Nina";
$a[]="Ophelia";
$a[]="Petunia";
$a[]="Amanda";
$a[]="Raquel";
$a[]="Cindy";
$a[]="Doris";
$a[]="Eve";
$a[]="Evita";
$a[]="Sunniva";
$a[]="Tove";
$a[]="Unni";
$a[]="Violet";
$a[]="Liza";
$a[]="Elizabeth";
$a[]="Ellen";
$a[]="Wenche";
$a[]="Vicky";
//get the q parameter from URL
$q=$_GET["q"];
//lookup all hints from array if length of q>0
if (strlen($q) > 0)
{
$hint="";
for($i=0; $i<count($a); $i++)
{
if (strtolower($q)==strtolower(substr($a[$i],0,strlen($q))))
{
if ($hint=="")
{
$hint=$a[$i];
}
else
{
$hint=$hint." , ".$a[$i];
}
}
}
}
//Set output to "no suggestion" if no hint were found
//or to the correct values
if ($hint == "")
{
$response="no suggestion";
}
else
{
$response=$hint;
}
//output the response
echo $response;
?>
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If there is any text sent from the JavaScript (strlen($q) > 0) the following
happens:
- Find a name matching the characters sent from the JavaScript
- If more than one name is found, include all names in the response string
- If no matching names were found, set response to "no suggestion"
- If one or more matching names were found, set response to these names
- The response is sent to the "txtHint" placeholder
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