Ciao.
Prova con questo:
(l'esempio è molto ma è per rendere l'idea)
Pagina htm:
Codice PHP:
<HTML>
      <head>
            <title>PHP & Javascript - Example</title>
            <SCRIPT type="text/javascript">    
                  function attach_file( p_script_url ) {
                        // create new script element, set its relative URL, and load it
                        script = document.createElement( 'script' );
                        script.src = p_script_url;

                        document.getElementsByTagName( 'head' )[0].appendChild( script );
                  }
            </SCRIPT>
      </head>    
      <body>

            
            [url="javascript:attach_file( 'js.php' )"]Schizza[/url]
            


            <span id="dynamic_span" />
      </body>
</HTML> 
Pagina js.php:

Codice PHP:
<?php
# set appropriate content type - to tell the browser we're returning Javascript
header( 'Content-Type: text/javascript' );         
function js()
{
return 'inner_html';
}
?>
// retrieve span object, and attach additional HTML to it
dynamic_span_obj          = document.getElementById( 'dynamic_span' );
dynamic_span_obj.innerHTML     += '<?php echo js(); ?>';