The default syntax starts with "<? php" and ends with "?>".
<?php echo "Default Syntax"; ?>
Short open Tags
The short tags starts with "<?" and ends with "?>". Short style tags are only available when they are enabled in php.ini configuration file on servers.
<? echo "PHP example with short-tags"; ?>
Omit the PHP closing tag at the end of the file
It is recommended that a closing PHP tag shall be omitted in a file containing only PHP code so that occurrences of accidental whitespace or new lines being added after the PHP closing tag, which may start output buffering causing uncalled for effects can be avoided.
<?php echo "PHP example with short-tags";