Run this from SSH
php -i 'phpinfo();' | grep 'Configuration File'
That will tell you where the php.ini file is.
A lot of times if you have Zend installed your config file is located at
/usr/local/Zend/etc/php.ini
And if you do a php upgrade, asl fix, psa/plesk update it will over write your symbolic link with a small amount of lines.
You can fix that by doing this:
cd /etc
rm -Rf php.ini
ln -s /usr/local/Zend/etc/php.ini php.ini
then do
php -v
and make sure php works, and you can redo the SSH line from above to make sure the ini file works. All of those steps are making assumptions that your files are int he same places, change the locations to suit your needs if they are some where else.