“Access denied for user ‘username’@’hostname’ (using password: YES)” – Error while connecting MySQL with PHP

The Problem

If the MySQL password contains a dollar sign character ‘$’, PHP is unable to connect and issues an error like:

Access denied for user 'username'@'hostname' (using password: YES)

Connections via other clients work correctly.

The Solution

PHP interprets dollar signs inside of double quotes as starting a variable name, which will be expanded. This expansion will change the password sent to MySQL.

There are 3 ways to avoid this problem:

1. Escape the character with a backslash: “pa\$\$word” (actual password being pa$$word)
2. Use single quotes: ‘pa$$word’
3. Avoid using the ‘$’ character in the password.

To help detect this kind of problem, a good practice is to run PHP with error reporting enabled and set to include E_STRICT (or E_ALL for PHP versions 5.4.0 and later). This setting will notify you of an undefined variable, which may reveal the problem.

PHP Error Levels

PHP provides several built-in constants for describing different error levels. Table below includes some of the more important ones.