Converting Image Files in PHP
How do you convert one image files to another using server side script ?
Simple, use ImageMagick. It will convert practically any image filetype to another. It is a command-line script. So, you need to have it installed on your web server. Something difficult to do on shared hosting.
If you do manage, though, the PHP Manual do have built-in function for interaction. It does require minimum PHP 5.1.3 and ImageMagick 6.2.4.
Should you prefer not to use the built-in function, you can simply pipe the command to exec().