How to show image larger when i put cursor in image in php?

Hello,

I have a image with size 48 by 48 when i put cursor in it i should get large image..

Here is my code..

<li><a href="/student/student/'.$oStudent->Guid.'">
<span class="icon"><img src="'.$sStudentImage.'" height="48" width="48" /> </span>'name'</a></li>

please help me out,,

Thanks alot.....
kiran