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PHP - AJAX and PHP


AJAX is used to create more interactive applications.


AJAX PHP Example

The following example will demonstrate how a web page can communicate with a web server while a user type characters in an input field:

Example

Start typing a name in the input field below:

First name:

Suggestions:




Example Explained - The HTML Page

When a user types a character in the input field above, the function "showHint()" is executed. The function is triggered by the "onkeyup" event:

<html>
<head>
<script>
function showHint(str)
{
if (str.length==0)
  {
  document.getElementById("txtHint").innerHTML="";
  return;
  }
var xmlhttp=new XMLHttpRequest();
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","gethint.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>

<p><b>Start typing a name in the input field below:</b></p>
<form>
First name: <input type="text" onkeyup="showHint(this.value)">
</form>
<p>Suggestions: <span id="txtHint"></span></p>

</body>
</html>

Source code explanation:

If the input field is empty (str.length==0), the function clears the content of the txtHint placeholder and exits the function.

If the input field is not empty, the showHint() function executes 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 input field)

The PHP File

The page on the server called by the JavaScript above is a PHP file called "gethint.php".

The source code in "gethint.php" checks an array of names, and returns the corresponding name(s) to the browser:

<?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
$q=$_REQUEST["q"]; $hint="";

// lookup all hints from array if $q is different from ""
if ($q !== "")
  { $q=strtolower($q); $len=strlen($q);
    foreach($a as $name)
    { if (stristr($q, substr($name,0,$len)))
      { if ($hint==="")
        { $hint=$name; }
        else
        { $hint .= ", $name"; }
      }
    }
  }

// Output "no suggestion" if no hint were found
// or output the correct values
echo $hint==="" ? "no suggestion" : $hint;
?>



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