Problem calling a js function from php

Question

I am using my php to call a js function like this:

<?php 
$chk=1;
if($chk==1)
{
    echo '<script>testing();</script>';
}
?>

and my js looks like:

function testing()
{
   document.getElementById("mainbody").innerHTML="This is my first JavaScript!";
}

The js is an external js file.

My html looks like:

<html>
<head>
<script src="qotw.js"></script>
</head> 
    <body>
    <div id="mainbody"></div>     
    </body>
</html>

but this is not working. What am i doing wrong over here? Please tell me if you know.

Best Zeeshan

include the html as output by your script - I suspect you just have something missing from it. — Paul Dixon
– Paul Dixon, Commented Jul 9, 2009 at 16:00
@Paul, why did you add the SCRIPT tags? Are you sure he makes use of them? — Ionuț G. Stan
– Ionuț G. Stan, Commented Jul 9, 2009 at 16:02
Paul, you're right. The original had SCRIPT tags, I had to click "view source" to see them. — Ionuț G. Stan
– Ionuț G. Stan, Commented Jul 9, 2009 at 16:05
The script is not being called. i tried echo '<script type="text/javascript">alert("hello");testing();</script>'; and no alert came. — Zeeshan Rang
– Zeeshan Rang, Commented Jul 9, 2009 at 16:32

Quentin · Accepted Answer · 2009-07-09 16:06:08Z

7

You run the script before the div you are targeting exists, so the document.getElementById call returns a false value instead of an HTMLElementNode.

You either need to move the script element so it is after the div, or assign the function to an event handler (onload for instance) instead of calling it directly.

This has nothing to do with the use of PHP.

Incidentally, your HTML is invalid and triggers quirks mode.

edited Jul 9, 2009 at 16:06

answered Jul 9, 2009 at 15:58

Quentin

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2 Comments

Zeeshan Rang Over a year ago

No that is not happening. The div id=mainbody has a button inside it, onclick=the js is called and from that js further php is called.

Quentin Over a year ago

You can't call PHP from JS. PHP runs on the server, generates a document (containing JS), delivers it to the client, the client then runs the JS. It is too late for any more PHP to run at this point - a new HTTP request has to be made to the server. You appear to have reduced your test case too far and deleted some of the information needed to see all your errors.

Dave Archer · Accepted Answer · 2009-07-09 16:04:42Z

1

Try testing the following in order:
first: Your script is being called

<script type="text/javascript">alert("hello");testing();</script>

second: The function is being called

function testing() {
    alert('inside testing');
}

third: As suggested above,

if (document.getElementById("mainbody") == null) alert('yep, its null');

then let us know the results

answered Jul 9, 2009 at 16:04

Dave Archer

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1 Comment

Zeeshan Rang Over a year ago

The script is not being called. i tried echo '<script type="text/javascript">alert("hello");testing();</script>'; and no alert came.

David Hedlund · Accepted Answer · 2009-07-09 16:00:08Z

1

Make sure that 'testing' isn't called above 'mainbody' in the code, because then the code would be run at a point during load, when the object doesn't exist.

answered Jul 9, 2009 at 16:00

David Hedlund

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