Question

Possible Duplicates:
Are PHP short tags acceptable to use?
What does “<?=” mean when seen in PHP

is there any difference in using <? ?> to signify a php block, or using <?php ?> ?

if there is not, why would anyone use <?php ?

figure the file extension of .php would give plenty of info about what type of code you are looking at.

Answer 1

The first is called short-open tags and second one is safe open and close tags.
You could enable/disable short open tags in php.ini using short_open_tag setting.

The short tags should be avoided, have a look at:

PHP Short Open Tag: Convenient Shortcut or Short Changing Security?