MAMP 3.1 + Revo 2.3.3 = total failure

Here's the story.

Upgraded MAMP from 3.0.6 to MAMP 3.1

Revo 2.3.3 - can't connect to the database, have to use 127.0.0.1 as the database host. Installation continues successfully. Accessing the manager causes 503 not-found server error. Accessing the front-end causes the custom 500 error. All files and the database are installed correctly.

Revo 2.2.16 - requires 127.0.0.1 as the database host, installs and works as expected.

Evo 1.0.15 - installs and works as expected with no changes.

I had a similar problem. I was running Revo 2.2.14 successfully under MAMP 3.0, then upgrading to MAMP 3.1 caused my local Revo-served pages to give the custom 500 error.

A bit of searching led me to http://stackoverflow.com/questions/29267274/mamp-3-1-and-mysql-pdo and a bit more trial and error gave me a solution...

This worked for me:
Locate your php.ini file and add extension=pdo_mysql.so to the extensions section, then replace mysql.default_socket = /Applications/MAMP/tmp/mysql/mysql.sock with pdo_mysql.default_socket = /Applications/MAMP/tmp/mysql/mysql.sock
Copy the files 'pdo_mysql.a' and 'pdo_mysql.so' across from your earlier MAMP 3.0/PHP version install into your current MAMP 3.1/PHP version installation. For me the files were located in MAMP/bin/php/php5.6.2/lib/php/extensions/no-debug-non-zts-20131226/.

Restart MAMP 3.1 and hopefully that may do the trick?