The use of php “short tags”, for example:
<? echo "Hola Mundo!"; ?> is a bad and common practice
that many PHP developers still use.
The short tags format is only available using the function
short_tags() in PHP3 or activating the
short_open_tag in the php.ini configuration file(it comes activated by default). I do not recommend
to use it when you develop applications to redistribute or use in external servers because it can cause conflicts
for the user if short tags are not enabled.
In the official PHP manual and the Zend Framework manual, they recommend to not use “short tags” and it’s going to be fully deprecated in version 6 of PHP. Remember that code clearness is very important to a professional developer. Always use: <?php echo “Hola Mundo!”; ?>.