To determine if a measurement is less than or greater than another, use
compare(), which returns 0, -1 or 1 depending on the difference
between the two objects. Identical measurements will return 0. Lesser ones will return a
negative, greater ones a positive value.
Example 619. Difference
$unit = new Zend_Measure_Length(100, Zend_Measure_Length::CENTIMETER);
$unit2 = new Zend_Measure_Length(1, Zend_Measure_Length::METER);
$unit3 = new Zend_Measure_Length(1.2, Zend_Measure_Length::METER);