<?php$string = implode ( ",", // string $glue [ 0 => "lastname", 1 => "email", 2 => "phone", ] // array $pieces);?>
$string = 'lastname,email,phone'
'lastname,email,phone'
#1
implode
(",", [0 => "lastname", 1 => "email", 2 => "phone"])
#2
("hello", [])