Join array elements with a glue string.
Defaults to an empty string. This is not the preferred usage of implode() as glue would be the second parameter and thus, the bad prototype would be used.
Returns a string containing a string representation of all the array elements in the same order, with the glue string between each element.
$array = array('lastname', 'email', 'phone');
$comma_separated = implode(",", $array);
echo $comma_separated; // lastname,email,phone