image zooming using jquery and php

image zooming using jquery and php

I have two images in my folder one smaller and one is bigger.Smaller image
showing on frontend when i click on this smaller image ,bigger image will
come on another window by using jquery zoom function it is working in html
but not working with php here the jquery and php code please help me out
//Jquery zoom code
function zoom(photo, title,w,h)
{
var left = (screen.width/2)-(w/2);
var top = (screen.height/2)-(h/2);
var targetWin = window.open (photo, title, 'titlebar=0, toolbar=no,
location=no, directories=no, status=no, menubar=no, scrollbars=no,
resizable=no, copyhistory=no, width='+w+', height='+h+', top='+top+',
left='+left);
}
//php code
<?php
echo "<img src='./smaller/".$a."'
onClick=zoom('./bigger/".$a."',400,500); width='100px'
height='91px'>";
?>