Change mysql CLI call to native PHP function

[wojtekn]

It fixes #152

In this diff, I propose to change the way of validating MySQL connection from the CLI command call to the native PHP function.

$wpdb is not accessible, so I used the native mysqli function, similar to what happens in $wpdb->db_connect().

Testing steps

1. Prepare a directory that contains WordPress code
2. Remove wp-config.php if it exists
3. Try creating a config file using incorrect database credentials

../config-command/vendor/bin/wp config create --dbname=test --dbuser=test --dbpass=wrongpassword --locale=ro_RO --dbhost=127.0.0.1

4. Confirm that the error is shown and mentions incorrect credentials, e.g.:

Error (1045) Access denied for user 'test'@'172.17.0.1' (using password: YES)% 

5. Run the command with the correct database credentials
6. Confirm that the config file was created and success message was displayed:

Success: Generated 'wp-config.php' file.

[kozer]

@wojtekn , can you please provide some test instructions here?

[adamziel]

Suggested change

	die( 'Error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error() );
	die( 'Database connection error (' . mysqli_connect_errno() . ') ' . mysqli_connect_error() );

[dmsnell]

I've read some caution against using @ too liberally, and I think part of the reason is that error handlers still execute, and also that it can trap errors that we don't want to trap.

Not that it would demand any blocker on this PR, but it could bring some benefit to try and catch this in some other way. Potentially by setting mysqli_report( MYSQLI_REPORT_STRICT ) we could wrap this in a try block and bypass generating warnings while also only trapping errors related to the connection.

mysqli_report( MYSQLI_REPORT_STRICT );
try {
	mysqli_real_connect( … );
} catch ( mysqli_sql_exception $e ) {
	die( "Database connection error ({$e->message})" );
}

[wojtekn]

Thanks, I've adjusted the code based on the proposed approach.

[dmsnell]

it would be awesome here if we provided a description in a comment explaining why the command is calling a restricted function, similar to what's in the PR description.

[dmsnell]

I'm not sure who should review this, but from my perspective it looks like a positive change.

[danielbachhuber]

Amazingly, this seems to work fine against all PHP versions we support. Thanks for the pull request!