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AJAX is used to create more interactive applications.
The following example demonstrates how a web page can communicate with a web server while a user types characters in an input field:
Start typing a name in the input field below:
In the example above, when a user types a character in the input field, a function called showHint() is executed. The function is triggered by the onkeyup event.
Formula
< p > Start typing a name in the input field below:</p >
< p > Suggestions: < span id ="txtHint"></span ></p ><form> First name: <input type="text" onkeyup="showHint(this.value)"> </form> <script>
function showHint(str) {
if (str.length == 0) {
document.getElementById("txtHint").innerHTML = "";
return;
} else {
const xmlhttp = new XMLHttpRequest();
xmlhttp.onload = function() {
document.getElementById("txtHint").innerHTML = this.responseText;
}
xmlhttp.open("GET", "gethint.php?q=" + str);
xmlhttp.send();
}
}</script>
First, check if the input field is empty (str.length == 0). If it is, clear the content of the txtHint placeholder and exit the function. However, if the input field is not empty, do the following:
Create the function to be executed when the server response is ready Send the request off to a PHP file (gethint.php) on the server Notice that q parameter is added gethint.php?q="+str The str variable holds the content of the input field The PHP File - "gethint.php" The PHP file checks an array of names, and returns the corresponding name(s) to the browser: <?php // 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 was found or output correct values echo $hint === "" ? "no suggestion" : $hint;?>