$arr = array ( 0 => "lorem", 1 => "ipsum", 2 => "dolor");
$str = implode (", ", $arr);
$tags = implode(', ', array('tag1','tag2','tag3','tag4'));
$string = implode(', ', $tags);
$number = 8887;
echo number_format($number);
//Output:-
//8,887
Array to comma separated string