PHP tag in post content makes wordpress go crazy

If you only want the php code to be output without executing it, just escape the < signs by replacing it with the html entity &lt;.

&lt;?php

Like this, the tag will not be recognised and will be output as <?php.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)