Insert into two table foreign key and primary key - php

Question

I have two tables in my database namely reservations and guests. The rows are as follow:
Reservation:
Reservation id
Property Id
Checkin date
Checkout date
Price
Guest
Guest id
Reservation id
Guest name
Guest address
Using a form that contains the reservation details and the guest details at the same time.
How can I run the insert query so that the auto generated reservation id(auto-increment in database) can also be inserted into the guest table at the same time?
This is what I have so far. I changed my code using last_insert_id()
INSERT INTO reservations
SET Checkin date= '24/05/2018', checkout date = '29/05/2018';
INSERT INTO guests
SET reservation id = LAST_INSERT_ID(),
guest name = guest name

Answer 1

First insert to reservation table
<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sqlR = "INSERT INTO Reservation(firstname, lastname, email)
VALUES ('John', 'Doe', 'john#example.com')";
$rStatus = $conn->query($sqlR);
$res_id = $conn->insert_id;
$sql = "INSERT INTO MyGuests (firstname, lastname, email,res_id)
VALUES ('John', 'Doe', 'john#example.com',$res_id)";
if ($conn->query($sql) === TRUE) {
$last_id = $conn->insert_id;
echo "New record created successfully. Last inserted ID is: " . $last_id;
} else {
echo "Error: " . $sql . "<br>" . $conn->error;
}
$conn->close();
?>

Answer 2

Firstly you can insert the data into the Reservation table, based on the last inserted id, you can use the value for the column Reservation id for the table Guest. Also, please maintain foreign key constraints, so as on update and delete operations of Reservation, simultaneous operations are performed on the Guest table.
To get the last inserted id,
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "INSERT INTO ...";
if ($conn->query($sql) === TRUE) {
$last_id = $conn->insert_id; //gives the last inserted id
}

Answer 3

Run the insert query first with the insert_id function and then use that insert_id to run the second insert query