The current style guide says that you should shorten control structures (if) by doing the various conditional checks ahead of time. The problem is this stops short-circuiting which can both be a major boon for performance, and can be used for explicit behavior control, which we actually do in almost every file:

defined('MOODLE_INTERNAL') || die();

This relies on short-circuiting to work at all.

The example giving in the style guide if even an example of a unneeded performance hit:

$coursecategory = ($element['object']->is_course_item() or $element['object']->is_category_item());

$scalevalue = in_array($element['object']->gradetype, array(GRADE_TYPE_SCALE, GRADE_TYPE_VALUE));

if ($coursecategory and $scalevalue) {

The in_array() is now done every time, even if the first part of the check fails and it will never be used.

We should have a policy that allows the wrapping of large control structures, and give guidance about things like where you place the operators (start of end of line), parentheses, etc.