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basically I am trying to call a javascript function from my PHP and I am using code I know works in other situations however here is it not and I am at a loss as to why?

It may be something stupid as I have been staring at this screen for a long time :)

here is where I call the function:

if(isset($test_details['done_test'])){
    echo "getting here";
    echo "<SCRIPT LANGUAGE='javascript'>user_error();</SCRIPT>";
}

I successfully get 'getting here' printed however it does not call the JS function.

javascript function:

   function user_error(){
   document.write("working");
        //alert("User has already taken this test. Your are being redirected...");
        //setTimeout("window.location='home_student.php'",3000);
   }

The commented it what I do eventually want it to do.

Could anyone please shed some light.

Many thanks,

@Crimson - Here is what I tried after your advice...still no luck.

javascript now:

$(document).ready(function () {
     var done = "<?= $test_details['done_test'] ?>";
     if(typeof done != 'undefined'){
          $('WORKING').appendTo('#bodyArea'); // just to test
     }
});
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  • 2
    remember you're not really calling it from PHP -- you're generating part of an HTML document that's than calling your JS function. Can you link to the final output document, or provide it in your question? The fact you're writing the script tag via PHP is largely irrelevant. Commented Apr 20, 2011 at 21:32
  • does the js function work when you call it in plain html? Commented Apr 20, 2011 at 21:34
  • 1
    The order of the code is important here, the latter, javascript function has to be declared before the call in the first code block of the generated html document. The order of your examples is so to say, incorrect ;) Commented Apr 20, 2011 at 21:34
  • 2
    Note that the language attribute is deprecated. You should use type="text/javascript" instead. Can you turn on Firebug and see if you get any JavaScript errors elsewhere? Commented Apr 20, 2011 at 21:35
  • @Caspar Kleijne, that is the issue, I am new to programming, so I didn't know this. Commented Apr 20, 2011 at 21:38

3 Answers 3

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By echoing <script>...</script> with PHP, you are not going to get the browser run the JS function!

PHP only outputs the HTML file that you want to send to the browser. The browser then parses this HTML and does a multitude of things before the page is displayed to the user.

Next, the user interacts with the displayed page (or some other browser related event like 'onload' happens) and the attached JS gets called.

So, if there is some JS that you want to run at a certain time, say immediately after the browser has finished loading the page, you need to create JS in the HTML file such that there is a JS function which gets called at the page load event like this:

<body onload="/*do something here*/"> ... </body>

It is better to use JQuery or some other JS frmework to accomplish something like this though.

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9 Comments

Anything inside a <script> tag is going to get executed whenever the browser encounters it while parsing the page. Moving it to an onload handler simply changes when the call happens. it may be that his user_error function hasn't been loaded yet, but fundamentally, there's nothing wrong with how he's going abou tit.
i've identified the fact that I am trying to call the function before the script has been parsed. Still I am faced with the issue I want to make this check on loading the page and make use of javascript.
@Andre: It is always better to use a framework because different browsers execute 'body onload' at different times and many times 'body onload' is called when the script hasn't been loaded. This is precisely why frameworks like Jquery have the basic 'ready' functions. All JS/JQuery code is practically written inside one such 'ready' function.
@buymypies: use Jquery - $(document).ready(function(){/*whatever*/}). See more at api.jquery.com/ready
@Crimson: but with this, I still want to run a mysql query first to get the value I want to check, then I want to make use of the javascript/jquery.
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Are you sure the function is already defined? Perhaps you declared your function after making the function call.

Additionally, although it's not really going to matter here, the proper way to have a javascript script tag is.

<script type="text/javascript"></script>

i.e. not language="javascript"

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Replace the line you call the JS function with this:

echo '<script type="text/javascript">window.onload = user_error </script>' ;

It should solve the problem. Because at the time you are calling user_error(), the function may not have been initialized by the browser. So you'll get an error since the function could not be found.

If the function is placed in an external .js file, it's very likely that you get this error, since the external file usually takes a while to be loaded. If the function deceleration is in the same file but after where you are calling it, same thing happens.

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if you look at my updated post, I changed my method to use that jquery however still no luck :S

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