Best Way To Concatenate Strings In PHP With Spaces In Between

Question

I need to concatenate an indeterminate number of strings, and I would like a space in between two adjoining strings. Like so a b c d e f.

Also I do not want

Answer 1

I just want to add to deviousdodo's answer that if there is a case that there are empty strings in the array and you don't want these to appear in the concatenated string, such as "a,b,,d,,f" then it will better to use the following:

$str = implode(',', array_filter(array('a', 'b', '', 'd', '', 'f')));