Well, I'm not sure what you mean exactly. As the other author correctly stated, PHP is server side and Javascript is client side.
So; when your code is parsed, the PHP part will be done first (by the server) after that, the code is send to the browser (visitor) upon loading in the browser, the javascript code is parsed.
E.g:
Server side = the webserver
Client side = the browser/visitor of your page
With this in mind, you cannot execute script function, since the javascript is not available to the browser while the PHP code is parsed by the server. However, you can do something like this:
<?
echo "<input type=\"text\" name=\"test\" OnChange=\"scriptfunction();\" />";
?>
With this in mind, you could write browser specific javascript and trigger it like this:
<?
if ( $browser_ie ) {
$execute = "script_ie();";
} else {
$execute = "script_other();";
}
?>
Which would change your source into this:
<?
echo "<input type=\"text\" name=\"test\" OnChange=\"" . $execute ."\" />";
?>
I hope this makes sense, and most of the code examples will make it through the filters of this forum ;-)