TypeError：$（selector）为null

I have a web page that redirects to another page on click. On the second page I have this:

<?php if(isset($_POST['tab1'])) { ?>
  <script>$('#home').trigger('click'); </script> 
<?php }?>

The $_POST comes back ok, only I get this error in the console for the jquery:

In firebug:

TypeError: $("#home") is null

Or in Chrome:

$('#home').trigger('click');

If I run this: alert(document.getElementsByTagName('#home'));

I get a alert with: [object HTMLCollection] as undefined

If I view the source I can see my jquery there:

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.js"></script>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.8.16/jquery-ui.js"></script>
<script>
!window.jQuery && document.write('<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.js"><\/script>');
</script>

Any ideas on why the jquery fails?

Try putting it in a document ready to ensure that the DOM is loaded before manipulating it:

<?php if(isset($_POST['tab1'])) { ?>
    <script>$(function() { $('#home').trigger('click'); } );</script>
<?php }?>

FIX:

   <script>$( window ).load(function() { $('#home').trigger('click'); });</script>

Put your script in the ready() function. Try something like this:

<?php if(isset($_POST['tab1'])) { ?>
  <script>$(function(){
           $('#home').trigger('click');
   });</script> 
<?php }?>

Assuring the document loads first is critical.

<script>$(function() { $('#home').trigger('click'); });</script>

That's because by the time the script is loaded, it may be possible that #home isn't defined yet (because the source code defining it has not yet been downloaded/parsed),
so you should make sure by enclosing it with $(function() { ... }); or $(document).ready(function() { ... });

in some setups the $ sign is not an alias for jQuery
(ex. jQuery.noConflict(); causes that)

so $(document).ready(function() { ... }); is written

jQuery(document).ready(function() { ... });

In my case, the unique solution that worked is this one I've got from here:

<script language="javascript" type="text/javascript">
  var $j = jQuery.noConflict();
  $j(document).ready(
    function() {
      alert($j("selector")); //object is properly initialized
    }
  );
</script>

Use the jQuery.noConflict(); return variable instead of $.