For those of you who don't know, "universal constructor" is the name I give to PHP constructors that always and only take a single parameter. The parameter is an array of key-value pairs, which is then merged with a set of default keys and values. Finally, the array is unmarshalled, usually into object properties.
One benefit of the universal constructor is that it allows you to quickly and easily pass in configuration values from a config file (or other source) when building an object. You don't have to remember the order of parameters, and you only need to specify the values that override the defaults.
I standardized on a universal constructor in the Solar framework for PHP. As far as I know, Solar was the first to standardize on this pattern and give it a name, and other PHP projects appear to be adopting the idea based on my advocacy. I saw a link today to a universal constructor "in the wild", not the result of my direct advocacy, here: http://www.jqueryin.com/projects/mongo-session/.
It's nice to see the idea is getting around.