Assumes MAMP was installed to default location: /Applications/MAMP
.
$> ln -s /Applications/MAMP/bin/php/php5.2.17/bin/php /usr/local/bin/php52
$> php52 -v
PHP 5.2.17 (cli) (built: Jan 21 2013 14:44:43)
Copyright (c) 1997-2010 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2010 Zend Technologies
with eAccelerator v1.0-dev, Copyright (c) 2004-2012 eAccelerator, by eAccelerator