In php, can both and. be used as connectors?

Question

I watched Teacher Zhu’s introductory video today and found that sometimes I use echo key($arr).'=>'.current($arr).'<br>'; Sometimes I use echo key($arr) , '=>', current($arr), '<br>';, can all be parsed normally. Do the "." and "." here all function as connectors?

Answer 1

The string concatenation character in php is "."

echo can output multiple values ​​separated by ","