How to convert php array?

Question

PHP

How to convert an array to php, let's say $arr=array('1','2','3','4','5','10','11','15','20');
In the line: "1-5, 10-11, 15, 20"
i.e. from the elements following in order, make gaps

Answer 1

How to make a sequence of arrays? - the answer to exactly the same question.

Answer 2

Iterate with for, form a new array. If the previous element differs by 1, we form a gap, if not, we fuck it as it is.