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Detect AJAX Request

The HTTP_X_REQUESTED_WITH header is sent by all recent browsers that support AJAX requests.

if ( !empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest' )
{
       # Ex. check the query and serve requested data
}

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  1. Frank

    I think isset() is more appropriate than !empty() in this situation. Still a useful snippet though. :)

    Reply ↓
  2. David

    So that you don’t get the notice about whether the variable is set or the attribute is set you should use both isset() and !empty().


    if (isset($_SERVER['HTTP_X_REQUESTED_WITH'] && !empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest')
    {
    # Ex. check the query and serve requested data
    }

    Reply ↓
  3. Dani

    great and practical snip, however, I’d like to know if there is a great or important disadvantage in using this approach when working with synchronized(normal request) and asynchronized(ajax request) requests in the same page.

    Reply ↓
  4. SmarterGuy

    The statement “The HTTP_X_REQUESTED_WITH header is sent by all recent browsers that support AJAX requests.” is 100% false.

    The browser does not send this header, javascript libraries do. Libraries like jquery, prototype and mootools.

    Reply ↓
  5. Suresh

    Hi guys,

    I want to check availability of internet connection before every AJAX request. If the connection is available – proceed else give a pop up message- net not available.

    I wrote the javascript to check net connection.But to check if a request is a AJAX request or a normal request if put following filter in my javaScript code:

    if (isset($_SERVER['HTTP_X_REQUESTED_WITH'] && !empty($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == ‘xmlhttprequest’))

    I got following error

    $_SERVER is not defined

    Can anyone correct me, if I am going wrong.

    Reply ↓
    • Will

      @Suresh, that’s PHP code you’re trying to run inside of JavaScript. $_SERVER is only available to PHP so you’re getting ‘undefined’

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