cek validasi email

pagi forum... Sebelum melakukan proses deposit, ingin cek email harus sudah ada di table members, penulisannya dimana ya?

// Adding Deposit
if($action == 'add_deposit') {

	$member_game_id = $_POST['member_game_id'];
	$jumlah_deposit = $_POST['jumlah_deposit'];
	$member_email = $_POST['member_email'];
	$member_nama_rek = $_POST['member_nama_rek'];
	$member_no_rek = $_POST['member_no_rek'];
	$member_bank = $_POST['member_bank'];
	$member_game = $_POST['member_game'];
	$tanggal = date("Y-m-d");
	$jam = date("h:i:s");
	$ip =  $_SERVER["REMOTE_ADDR"];

	//our insert query query
	$query  = "INSERT INTO deposit
				(
					member_game_id,
					jumlah_deposit,
					member_email,
					member_nama_rek,
					member_no_rek,
					member_bank,
					member_game,
					tanggal,
					jam,
					ip

				)
				VALUES (
					?,
                	?,
                	?,
                	?,
                	?,
                	?,
                	?,
                	?,
                	?,
                	?
                );
              ";

    header('Content-Type: application/json');

	/* Prepare statement */
	$stmt = $mysqli->prepare($query);
	if($stmt === false) {
	  trigger_error('Wrong SQL: ' . $query . ' Error: ' . $mysqli->error, E_USER_ERROR);
	}

	/* Bind parameters. TYpes: s = string, i = integer, d = double,  b = blob */
	$stmt->bind_param('ssssssssss',$member_game_id,$jumlah_deposit,$member_email,$member_nama_rek,$member_no_rek,$member_bank,$member_game,$tanggal,$jam,$ip);

	if($stmt->execute()){
	    //if saving success
		echo json_encode(array(
			'status' => 'Success',
			'message'=> 'Deposit Berhasil!'
		));

	} else {
	    //if unable to create new record
	    echo json_encode(array(
	    	'status' => 'Error',
	    	//'message'=> 'There has been an error, please try again.'
	    	'message' => 'There has been an error, please try again.'.$mysqli->error.'</pre>'.$query.'</pre>'
	    ));
	}

	//close database connection
	$mysqli->close();
}