I’m working on building an ideal server setup that allows for both PHP 4 and PHP 5 on Apache with suPHP (I’ll blog about this later). While testing my PHP 4 build, I got the following error:

Warning: mysql_connect() [function.mysql-connect]: Client does not support authentication protocol requested by server; consider upgrading MySQL client in /var/www/test-php.php  on line 3
Couldn't authenticate with MySQL

The code I used to test this is quite simple:

if ( false === ( $db = mysql_connect( 'localhost', 'username', 'password' ) ) )
    die( "Couldn't authenticate with MySQL" );

if ( false === mysql_select_db( 'database' ) )
    die( "Couldn't connect to database" );

echo "Yay!";

?>

After digging around for a bit, I found that mixing PHP 4 with a MySQL version greater than or equal to 4.1 causes this problem. MySQL 4.1 introduced a new password caching scheme that PHP 4 can’t work with.

The solution is to update the database user’s password using the OLD_PASSWORD function of MySQL. For example:

[chris@office ~]$ mysql -u root -p mysql
Enter password:
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 267
Server version: 5.1.41-3ubuntu12.1 (Ubuntu)

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> update user set Password=OLD_PASSWORD('password') WHERE User='username';
Query OK, 0 rows affected (0.02 sec)
Rows matched: 0  Changed: 0  Warnings: 0

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

mysql>

Note the underlined areas. That is where you’ll want to provide your own username and password.

Once you’ve followed these steps, both PHP 4 and PHP 5 will be able to communite with the database.

Thanks to digitalpeer for providing the answer to my issue.

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