Is there any problem if a PHP program contains a SUBMIT button who calls the same program again with different arguments?
Nope.
The only real problem (and this is nothing to do with PHP) is that pressing the browser refresh button causes the data from the previous page to be resubmitted, which can cause heachaches in some situations.
Thank you ahundiak, Shrike!
What can I suspect if pressing SUBMIT button once nothing happens and pressing it once again the page is displayed correctly, and this behavior is random?
Wait... after some research I've solved the problem by replacing mysql_pconnect() with mysql_connect().
Another question: why sometimes pictures in page are not displayed on first load but displayed after Refresh (F5) button is pressed?
