Get the value of a variable declared in a PHP function - php

Question

I have 2 pages, "signup.php" and "globalfunctions.php". On signup.php, I get all of the info from the form submission, I hash the password (by appending a random string generated in globalfunctions.php), and I use the function executeSQL that I defined.
signup.php:
include('/home/www/portaldev.samgoodman.co/processes/globalfunctions.php');
$singleAppendString = generateRandomAppend(16);
$form_email = $_POST['email'];
$form_password = $_POST['password'];
$form_name = $_POST['name'];
$form_school = $_POST['schoolid'];
$form_grad = $_POST['gradyear'];
$form_ip = $_SERVER['REMOTE_ADDR'];
$password_with_hash = $form_password.$singleAppendString;
$hashedPassword = sha1($password_with_hash);
executeSQL("$nextUserQuery", "SELECT id FROM users ORDER BY id DESC LIMIT 0 , 1");
Here is where I would like to get the value of $nextUserQuery from the database, but I need to return the value in the function.
executeSQL("$insertUser", "INSERT INTO users (id, name, email, password, school_id, grad_year, lvl, signup_ip) VALUES ('".$calc_userid."', '".$form_name."', '".$form_email."', '".$hashedPassword."', '".$form_school."', '".$form_grad."', '0','".$form_ip."')");
executeSQL("$insertHash", "INSERT INTO vault (id, hash) VALUES ('".$calc_userid."', '".$singleAppendString."')");
globalfunctions.php
function generateRandomAppend($length) {
$characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$randomString = '';
for ($i = 0; $i < $length; $i++) {
$randomString .= $characters[rand(0, strlen($characters) - 1)];
}
return $randomString;
}
function executeSQL($varName, $query) {
global $varName;
$con=mysqli_connect("localhost", "hugopak1_spm", "Massavailable1", "hugopak1_spm");
$varName = mysqli_query($con, $query);
return $varName;
}

Answer 1

What you currently do is not the correct way to get the value returned by executeSQL function. Remove $varName parameter from executeSQL function
function executeSQL($query) {
$con = mysqli_connect("localhost", "hugopak1_spm", "Massavailable1", "hugopak1_spm");
$varName = mysqli_query($con, $query);
return $varName;
}
and declare a new variable that will hold the returned value
$nextUserQuery = executeSQL("SELECT id FROM users ORDER BY id DESC LIMIT 0 , 1");
In the above example, the value of $nextUserQuery is the value returned by executeSQL("SELECT id FROM users ORDER BY id DESC LIMIT 0 , 1"). You should apply the same thing to the other two lines as below
$insertUser = executeSQL("INSERT INTO users (id, name, email, password, school_id, grad_year, lvl, signup_ip) VALUES ('".$calc_userid."', '".$form_name."', '".$form_email."', '".$hashedPassword."', '".$form_school."', '".$form_grad."', '0','".$form_ip."')");
$insertHash = executeSQL("INSERT INTO vault (id, hash) VALUES ('".$calc_userid."', '".$singleAppendString."')");