Not all of PHP installation has short tags support. There are a few installations that have turned it off. If the short tags are turned off, only <?php and <script> tags are recognized. The <? tags are not allowed and the scripts are broken.
If you want to use the PHP short tag <? you need to edit the php.ini file and set short_open_tag to on:
short_open_tag = On
Using short tags should be avoided when developing applications that are meant for redistribution, or deployment on PHP servers which are not under your control, because short tags may not be supported on the target server. Besides short tags are considered bad because they are in conflict with XML’s open tag ‘<?xml’.
For portable reason, redistributable code, be sure not to use short tags.
