JavaScript Dynamic content change

Dynamic content change

<?php
if(isset($_GET['sub'])) {
	echo "Second Text";
	exit(0);
}
?>
<img src='image.jpg' onClick="javascript:
	var xmlhttp=false;
    /*@cc_on @*/
    /*@if (@_jscript_version >= 5)
    try {
    	xmlhttp = new ActiveXObject('Msxml2.XMLHTTP');
	} catch (e) {
		try { xmlhttp = new ActiveXObject('Microsoft.XMLHTTP'); } catch (E) { xmlhttp = false; }
	}
	@end @*/
	if(!xmlhttp) { xmlhttp=new XMLHttpRequest(); }
	xmlhttp.open('GET','test.php?sub', true);
	xmlhttp.onreadystatechange = function() {
		if(xmlhttp.readyState==4) { document.getElementById('output').innerHTML = xmlhttp.responseText; }
	}
	xmlhttp.send(null);
">
<div id='output'>First Text</div>