This is my php for viewing user profile - php

Question

My Profile php
<?php
//profile.php
require_once 'includes/global.php';
//check to see if they're logged in
if(!isset($_SESSION['logged_in'])) {
header("Location: login.php");
}
// finding user and viewing it
$tools = new FindUser();
$user = $tools->get($_REQUEST['userID']);
?>
This is my php for viewing user profile.
http://mywebsite.com/profile.php?userID=5 its working fine in this way.
i want my code to check if user is available in database for example if i add ?userID=10 which is not present in database it gives out mysql error or even if i use http://mywebsite.com/profile.phpthen also it give error.
so now i want if user is not available in database it should give that user is not available and when we use simple http://mywebsite.com/profile.php it should give auto add it to userID=1 OR REDIRECT it to home.php
If there is other way of doing this please let me know. well im very newbie in this field
Thanks for looking my question and answering :)
Solved
<?php
//profile.php
require_once 'includes/global.php';
//check to see if they're logged in
if(!isset($_SESSION['logged_in'])) {
header("Location: login.php");
}
$UserID = $_GET['userID'];
$CheckQuery = mysql_query("SELECT * FROM users WHERE id='$UserID'");
$CheckNumber = mysql_num_rows($CheckQuery);
if ($CheckNumber !== 1)
{
header("Location: index.php");
}
// finding user and viewing it
$tools = new FindUser();
$user = $tools->get($_REQUEST['userID']);
?>

Answer 1

You shouldn't use MySQL As it's depreciated,
If you really wish to use MySQL You could check at the start of the script if there is a row count for the User ID, Example:
<?
$UserID = $_GET['UserID'];
$UserID = mysql_real_escape_string($UserID);
$CheckQuery = mysql_query("SELECT * FROM users WHERE userID='$UserID'");
$CheckNumber = mysql_num_rows($CheckQuery);
if ($CheckNumber !== 1)
{
// Do something If user is Not Found
// Redirect to Another Page OR Something
}
?>

Answer 2

than check that query give with result if it wont found data in database than redirect
$result = mysql_query(...);
if(mysql_num_rows($result) !=1){ //
header("Location:signup.php");
exit();
}
You shouldn't use MySQL As it's depreciated, either use PDO or mysqli