If you are using PHP 5.3.x on a UNIX or Linux system and the <? ?> tags are not working, it is likely that the short_open_tag setting in your PHP configuration is disabled.
By default, the short_open_tag setting is disabled in PHP 5.3.x and later versions. This means that you will need to use the <?php ?> tags to enclose PHP code, rather than the shorter <? ?> tags.
If you want to enable the use of the <? ?> tags, you will need to edit the PHP configuration file (usually php.ini) and set the short_open_tag setting to On.
To do this, open the php.ini file in a text editor and search for the short_open_tag setting. It should be set to Off by default. Change it to On and save the file.
Then, restart the web server to apply the changes.
short_open_tag = On
It's important to note that using the <? ?> tags is not recommended as they may not be supported in future versions of PHP. It is generally better to use the <?php ?> tags to enclose PHP code, as they are more portable and less prone to conflicts with other languages or systems.