For some reason the following code is causing a page I'm debugging to reload and start the debug session all over again, causing an infinite loop.
The value of $regs is a SQL date.
<?php
$date = explode('-',$regs[0]);
for( $i = 1; $i < 12; $i++ )
{
?>
<option value="<?= $i ?>"
<?php
if( $i == $date[1] )
{ print " selected"; }
?>
><?= $i ?></option>
<?php
}
?>
</select>&nbsp;

For some reason, when the $i reaches 11, the debugger reloads the page.

It may depend on the HTML and JavaScript you have in the file.
At some point, IE starts parsing HTML and executing the code even if the document is not complete. So if you have any "meta reload" or "
"document.location" statements, they may trigger browser to reload the page or forward to another location which subsequently trigger new debug session. Also it's possible that current debug session was timeouted by the browser. I'd recommend you to use breakpoints to execute your code faster.

But, this happens even when I single step through the code.

Look at the web server logs.
I think the answer is there.