The error
C.5.2.4. Client does not support authentication protocol
When using an older PHP version with PHP selector, like 5.2, is due to the version of MySQL not using the old password type (pre 4.1).
To fix this error, old passwords can be used.
On the server running in mysql
SET PASSWORD FOR ‘some_user’@’some_host’ = OLD_PASSWORD(‘newpwd’);
Will set the password to use the old password version.
When done run
mysqladmin reload