I have a localhost development environment using MAMP Pro, with a Wordpress website working successfully using PHP 5.6.8. Changing the host to PHP 7.0.13 (and changing nothing else) results in the error:
Warning: mysqli_real_connect(): (HY000/2002): No such file or directory in [edited path]/wp-includes/wp-db.php on line 1538
Error establishing a database connection
This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at localhost:3306. This could mean your host’s database server is down.
wp-config.php definitely has correct username, password, hostname and the database is running. Solutions to similar issues/warnings suggest the MySQL socket path in php.ini file could be wrong, but I have compared that file across the two php versions and they are the same.
I am using the latest versions of MAMP Pro (4.1) and Wordpress (4.7.4), as well as OS X (10.12.4). Also, the website works fine again when changing the host back to PHP 5.6.8.
No idea what else to do/check. Any thoughts are much appreciated.