Executing mysqli insert query then immediately selecting ID of new row - php

Question

I've been spending a couple of hours trying to write mysqli queries to insert a new row in a database (with a primary key ID) and then select the ID of the new row. My code as it currently is:
<?php
include('connectionData.php');
$conn = mysqli_connect($server, $user, $pass, $dbname, $port)
or die('Connection error');
if(isset($_POST['submit'])) {
$pnum = $_POST['pnum'];
$phone_insert_text = "INSERT INTO `voterdatabase`.`phone` (`pnum`) VALUES (?)";
$phone_insert_query = $conn->prepare($phone_insert_text);
$phone_insert_query->bind_param('s', $pnum);
$phone_insert_query->execute();
$phone_select_text = "SELECT phone_id FROM voterdatabase.phone WHERE pnum=?";
$phone_select_query = $conn->prepare($phone_select_text);
$phone_select_query->bind_param('s', $pnum);
$phone_select_query->execute();
$phone_select_query->bind_result($phone_id);
echo $phone_id;
?>
$phone_insert_query executes without issue. But $phone_select_query doesn't appear to run at all, as echo $phone_id; has no effect. What might be going on here? I'm able to run the query directly in MySQLWorkbench.
Note that I previously tried doing this in one query using SELECT LAST_INSERT_ID();, but mysqli fails to execute any query containing that.

Answer 1

Please try this
$lastInsertID= mysqli_insert_id($conn);

Answer 2

Use insert_id property:
<?php
include('connectionData.php');
$conn = mysqli_connect($server, $user, $pass, $dbname, $port)
or die('Connection error');
if(isset($_POST['submit'])) {
$pnum = $_POST['pnum'];
$phone_insert_text = "INSERT INTO `voterdatabase`.`phone` (`pnum`) VALUES (?)";
$phone_insert_query = $conn->prepare($phone_insert_text);
$phone_insert_query->bind_param('s', $pnum);
$phone_insert_query->execute();
$phone_id = $conn->insert_id;
echo $phone_id;
?>

Answer 3

If you wish to be able to use the available functions to get the last inserted id, like mysqli_insert_id(), your table must have an AUTO_INCREMENT column. If not you will not get the id.
Also, even if you have the required columns, this will require two calls. To get around this, what you could do is something like create a stored procedure to do your insert for you and return the inserted id from the procedure.