Although yes the problem is the php.ini file, ultimately, my issue was in using php straight out of the box on mac. Apparently, the default installation (in /usr/bin) is what's used from terminal, rather than the installation of PHP from mac. also, that default install doesn't have a php.ini file associated.
I found the following instruction from a forum for Yii, which was also playing up and turned out to be the same error:
A note on PHP and Mac OSX:
A version of PHP4 comes bundled on Mac OSX and is typically what is executed when you try the php command from the command line. You need to have the php command execute a version of PHP5.x or higher. Usually, you have already installed a version of PHP5.x or higher, but need to tell the php command to execute the newer version rather than the older one. There are certainly many ways to achieve this, but here is one:
at any terminal prompt, type in:
prompt>which php
this should tell you where the OS is looking for the php command
mine tells me /usr/bin/php
if I navigate to /usr/bin and issue an ls *php* I will see three files
php
php-config
phpize
These are all for the bundled version PHP4.x
rename these files to use a 4 in their names, to remember these are the executables for PHP4
mv php php4
mv php-config php-config4
mv phpize phpize4
Then, create sym links for each of these these to point to the PHP5.x or higher version you have installed. In my case these are located in /usr/local/apache/php/bin. So I would issue from the /usr/bin directory
ln -s [absolute path to your php5.x] php
and similarly for the other files.