Trouble with PEAR Capatcha

Hello. I am trying to write a form with capatcha but run into trouble. Below is what my error_log tells me. I am using LAMP on a Ubuntu Desktop. (Laters version) The link to the <img src="capatcha.php"> is broken or the error is in Line 42 that is like this: file_put_contents(md5(session_id()) . '.png', $png); [Thu Mar 31 16:28:39.294818 2016] [:error] [pid 10425] [client 127.0.0.1:41186] PHP Warning: file_put_contents(d41d8cd98f00b204e9800998ecf8427e.png): failed to open stream: Permission denied in /home/karl-arne/public_html/privat/s.php on line 42, referer: http://localhost/~karl-arne/privat/captcha_skjema.php karl-arne@karlarne-Lenovo-Z50-70:~/public_html/privat$ sudo ps aux | grep httpd [sudo] password for karl-arne: karl-ar+ 29230 0.0 0.0 17184 2212 pts/12 S+ 16:30 0:00 grep --color=auto httpd karl-arne@karlarne-Lenovo-Z50-70:~/public_html/privat$ I am using the example from http://pear.php.net/manual/en/package.text.text-captcha.example.php Thanks. Karl