The goal is to construct a comma separated string, using a loop but the same way $listtostring(var,",") would do (i.e. "a,b,c,d,e,f,g,h" without starting or ending comma).

What is the best way to do it, concerning the readability of the code and its performances?

To do so, there are more than 5 methods, but in this example we will test 4 :

1) using a "if" in the loop