$name = "Alice, Bob";
$names = explode(", ", $names);
var_dump($names);
//=>
// array(2) {
//   [0]=>string(5) "Alice"
//   [1]=>string(3) "Bob"
// }

$names = ['Alice', 'Bob'];
$names = implode(', ', $names);
var_dump($names); //=> string(10) "Alice, Bob"

var_dump(strlen('lorem')); //=> int(5)