My advice is to rely on a defined standard. I personally use the Zend Framework’s coding style.

So how to format the code? The first way is on the same line:

$myArray = array('key1' => 'value1',
		 'key2' => 'value2');

And the other, perhaps more clear way is to place the associative pairs on a new line:

$myArray = array(
	'key1' => 'value1',
	'key2' => 'value2',
);

Note that in the second example there’s a comma after the second pair. This is correct PHP syntax and is strongly encouraged!

It’s up to you which way to take. However it mainly depends on the case, but please use standards.