Having difficulty connecting to MySQL through PHP 5.3.x? Know that MySQL and PHP are properly configured? Using Windows Vista / 7? The problem may very well be that you’re connecting to ‘localhost.’ According to Joe Bedan, simply changing ‘localhost’ to ‘127.0.0.7’ will fix the problem, and he’s right!
According to another forum post, this is because Vista/7 does some goofy stuff with the ‘localhost’ alias. This person suggests that modifying the C:\Windows\System32\drivers\etc\hosts file to contain the line ‘127.0.0.1 localhost’ will fix the problem (make sure to do this as an administrator!). Unfortunately, this wasn’t the case for me. However, it’s worth a shot for anyone experiencing this problem.