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AJAX PHP

AJAX is used to create more interactive applications

AJAX PHP Example

The following example demonstrates how a web page can communicate with a web server while a user types characters in an input field:

Example

Start typing a name in the input field below:

Suggestions:

First name:


Example Explained

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.

Here is the code:

Example

<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?q=" + str);
  xmlhttp.send();
  }
}
</script>

Code explanation:

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 an XMLHttpRequest object
  • Create the function to be executed when the server response is ready
  • Send the request off to a PHP file (gethint) on the server
  • Notice that q parameter is added gethint?q="+str
  • The str variable holds the content of the input field

    • The PHP File - "gethint"

    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;
    ?>

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