php 5.2.x and short open tags
Those who have not worked on 5.2.x yet and comfortable with using <? ?> tags instead of <?php ?> tags, they might face weired issue of php processing. No error will generate and after check source of file, they will find php written rather processed data. One of the issue due to this weired error could be short_open_tag which is by default OFF now so scripts which use <? as start tag will not be processed by php engine. SO either change your start tag to <?php which is recommended now or set short_open_tag=ON.