PHP (If not existant in records.) [closed] - php

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So basically I got this code right here:
<?php
include_once 'dbconfig2.php';
$con = new DB_con();
$table = "users";
if(isset($_GET['profile_id']))
{
$sql=mysql_query("SELECT * FROM users WHERE user_id=".$_GET['profile_id']);
$result=mysql_fetch_array($sql);
}
?>
I am clueless as to how I would make it so if the user_id is not existent in the records, they cannot view their profile but it leads them to another messsage or piece of code.

Answer 1

If the user_id doesn't exist, there won't be any rows in the result. When you try to read a row with mysql_fetch_array(), it returns FALSE. So you can simply test $result:
if (!$result) {
die("Invalid profile ID");
}

Answer 2

Try to use prepared statements using mysqli, in order to avoid sql injection.
By way of example:
$mysqli = new mysqli("localhost", "root", "root", "test");
if ($mysqli->connect_errno) {
echo "connect_error". $mysqli->connect_error;
}
$id = $_GET['profile_id'];
$result = $mysqli->prepare('SELECT name FROM users WHERE user_id = ?');
$result->bind_param("i", $id);
$result->execute();
$result->bind_result($col1);
$result->fetch();
$is_valid_profile = (!$col1) ? 'Invalid profile' : 'Valid profile';
echo $is_valid_profile;
$result->close();
http://php.net/manual/en/mysqli.prepare.php