PHP Judge Ajax Request: Http_x_requested_with

PHP determines the principle of Ajax requests:

When sending an AJAX request, we can create a custom header message by XMLHttpRequest This object, in the jquery framework, for the $.ajax, $.get, or $.post methods that request the content of the Web page. It will pass a http_x_requested_with parameter to the server, PHP is in the header layer to determine whether the AJAX request, corresponding to $_server[' Http_x_requested_with '] judgment.

    /* * * whether the      current request is an AJAX request      *      * @access public      * @return BOOL      */     function Isajax ()     {         returnisset($_serverstrtolower($_server[' Http_x_requested_with ']) = = ' XMLHttpRequest ';     }

• In general $_server[' Http_x_requested_with ') is XMLHttpRequest by default
• $_server[' Http_x_requested_with ' can also be custom created, using Xmlhttprequest.setrequestheader (name,value); Reference article:/http www.skygq.com/2011/01/04/php-check-request-from-ajax-or-normal/

PHP cross-domain issues when judging Ajax requests:

If this is a cross-domain, the above isajax is completely incorrect. Cross-domain Problem reference: "Several problems encountered by $.getjson" use $.getjson to implement cross-domain, but detect whether Ajax is always false, and try to $get (see: $.get implementation returns parsing JSON data and JSONP cross-domain) after no results , consider using the universal $ajax method, see the documentation for Ajax:

If a script or JSONP type is specified, then when the data is received from the server, the <script> tag is actually used instead of the XMLHttpRequest object. In this case, $.ajax () no longer returns a XMLHttpRequest object, and it does not pass an event handler, such as Beforesend.

Explain:

Ajax can only specify JSONP format data, this is not XMLHttpRequest object, even if you customize a $_server[' Http_x_requested_with '] is meaningless

The solution:

For cross-domain scenarios, Getjson or Ajax (JSONP) can use the Accept Request header format to determine

PHP side corresponding $_server[' http_accept ']

Jsonp's request is generally: Text/javascript, Application/javascript, */*

JSON request: Application/json, Text/javascript, */*

A simple judgment for Ajax requests across domain conditions:

    Switch($_server[' Http_accept ']){           Case' Application/json, Text/javascript, */* '://JSON Format             Break;  Case' Text/javascript, Application/javascript, */* '://JavaScript or JSONP format             Break;  Case' Text/html, */* '://HTML Format             Break;  Case' Application/xml, Text/xml, */* '://XML Format             Break; }

PHP Judge Ajax Request: Http_x_requested_with