Don't use preg_replace for removing trailing words in strings

Currently in some places we are using mentioned later code to strip trailing word from string:

$pos_sql = preg_replace('/(.*) OR $/', '
1', $pos_sql)

This is not very efficient and should be replaced with code like this:

$pos_sql = substr($pos_sql, -2); // "-2" is "(-1) * strlen('OR')"