How to insert php code in posts?

Try RunPHP plugin as wp-exec is fairly limited as to what it will allow and RunPHP is more “open”. But it also depends upon how you are using the PHP within the post. In general, you can’t without one or both of these plugins. You might want to consider going straight to the source (either by clicking the edit source or whatever it is called in the Mudbomb plugin or by turning the plugin off for this usage.)

I have try runphp and phpexec and i can’t insert php code in my posts, i don’t know where is my problem, i’m running wp 1.5 with WYSIWYG plugin also, what can i do?