How to handle failed to open stream error, help (javascript, ajax)

Question

Hi,

I am working on a page that concurrently calls 3 (or more) of the same jscript function. I am using a function that is tested and works with multiple concurrent ajax requests (found on the web, it works because I am now facing this new problem).

The html is just this

<div  id="1"> <script> ajax2(); </script> </div> 
<div  id="2"> <script> ajax2(); </script> </div> 
<div  id="3"> <script> ajax2(); </script> </div> 

As you can see, the html requests 3 simultaneous calls to an identical function.

The ajax2() jscript function has this line to request an open of a file

xhrObj.open("GET", "../testa.php",true);

The problem is that sometimes the file is not available to be opened because of too many simultaneous requests, and the program gives a

Warning: Unknown: failed to open stream: Permission denied in Unknown on line 0 

Fatal error: Unknown: Failed opening required 'C:/xampp/htdocs/test/testa.php'

How do I handle this error and substitute the open file request so that it would open another file (ie testb.php)?

I tried to handle the substitution with the method of using testb.php and testc.php as substitutions for testa.php if testa.php is not available.

var x = xhrObj.open("GET", "../testa.php",true);
if (!x) { var y = xhrObj.open("GET", "../testb.php",true);
          if (!y) { xhrObj.open("GET", "../testc.php",true);}
}

but the code does not work. The syntax is wrong, because it gives the same error and the warnings show that testa.php is always the file that is not available.

What is the correct syntax for checking whether the xhrobj.open is OK, and if not, open another file?

TIA

Answer 1

You are making an asynchronous request, which means that you only start the request, and the method returns immediately without knowing if the request will work or not.

You either have to use the callback method that is called when the response arrives, or you have to make a synchronous request instead.