mysql views get decreased - php

Question

I own a image hosting website and I capture image views using php and mysql.
I use the following code to count the views.
include 'mysql.php';
$result = mysql_query("SELECT * FROM DB WHERE ID='$id'");
$row = mysql_fetch_array($result);
$views=$row['views'];
$query = "UPDATE DB SET views=$views+1 WHERE ID='$id'";
$result2 = mysql_query($query);
mysql_close($con);
views is mediumint(9) type field.
I noticed that the views get decreased day by day.can anyone say what is the problem and offer a solution.
Thanks.

Answer 1

You should use this to update instead:
$query = "UPDATE DB SET views=views+1 WHERE ID='$id'";
If a page takes a long time to execute, you can have one query overwrite another. Also using this, you might not need to even run the first query - unless you want other info from it.
The reason you are getting an error is that one script is reading the data and grabbing the value, then updating it - based on the value it is storing - but in the meantime other scripts could be updating the row. You could avoid it by using transactions, but that seems utter overkill for what you are doing.

Answer 2

You need to stop using mysql_* as those functions are deprecated
You don't need to make 2 queries just to increment a field by 1:
$query = "UPDATE DB SET views=views+1 WHERE ID='$id'";
and PDO example:
$db = new PDO('mysql:host=localhost;dbname=mydb;charset=UTF-8', 'username', 'password', array(PDO::ATTR_EMULATE_PREPARES => false, PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
$stmt = $db->prepare("UPDATE DB SET views=views+1 WHERE ID=:id");
$stmt->execute(array(':id' => $id));
Read more about prepared statements and PDO