Debugging PHP
Yesterday I noticed that certain wp-admin PHP pages were not accessible anymore. I was able to view messages but not to post them or change options. Originally I thought that this was the side effect of having two versions of Wordpress running at the same time or improper DB charset configuration of the second instance (I recently set up the Russian version of my blog). I tried to reinstall the latter instance with proper configuration and language but this didn’t help. HTTP fiddler showed no response from the server for problem PHP pages. I also noticed that my other domains running on the same server didn’t have this problem. Finally I hit upon the clue: one of logs had this error:
[client xx.xx.xx.xxx] PHP Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 11 bytes) in […] dumpanalysis.org/httpdocs/ru/blog/wp-admin/includes/update.php on line 17
Out of memory error! Googling “PHP memory” hit upon the solution to add the following line to .htaccess file:
php_value memory_limit 20M
Now it all suddenly made sense to me. I didn’t think of possible artificial memory limits in script engines. Adding the second instance of Wordpress hit PHP memory limit which was already almost exhausted by my Wordpress blog with more than 500 posts, Drupal portal, phpBB forum and MediaWiki.
Now I’m able to write posts again 
Happy debugging!
- Dmitry Vostokov @ DumpAnalysis.org -