MySQL Error mysqli::__construct(): (HY000/2002): Connection refused - php

Question

I'm trying to run a PHP Script that contains a MySQL connection, when I run the command I get the following error in the terminal:
'Warning: mysqli::__construct(): (HY000/2002): Connection refused'
Even with PDO, I get the error:
'Fatal error: Uncaught PDOException: SQLSTATE[HY000] [2002] No such file or directory in ...'
I'm running the script on Mac OS X, and I have MAMP as APACHE/MySQL local server.
The command that I use for running the script is:
'php main.php'
and the content of the 'main.php' file with PDO is:
$db = new PDO('mysql:host=localhost;dbname=test',root,root);
with mysqli connector:
$db = new mysqli("localhost", "test", "root", "root");
I tried with '127.0.0.1' instead of 'localhost' and I get the same errors in both cases.

Answer 1

First of all, using localhost as a domain name is not supported in PHP. It will not be resolved as 127.0.0.1.
Second, even using 127.0.0.1 might not work in servers with multiple interfaces or with special routing rules. Run mysqlcheck --help and take the IP address shown at the bottom in the "host" field. For example:
port 3306
host 192.168.1.23
Use the IP and port that MySQL recognizes:
$db = new mysqli("192.168.1.23:3306", "test", "root", "root");