PHP $_GET['id'] and security [duplicate] - php

Question

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How can I prevent SQL injection in PHP?
(27 answers)
Closed 9 years ago.
I have links on my webpage like this: http://test.com/index.php?function=news&id=88
So whenever I put a ' after 88, I get the following error: Warning: mysql_fetch_row() expects parameter 1 to be resource, boolean given in ... line 588
So I read about mysql_real_escape_string(), but I'm getting the ID not posting and I have no clue how should I prevent getting this error.
function news()
{
$query = mysql_query("SELECT * FROM news WHERE id=".$_GET['id']."");
while($news = mysql_fetch_row($query))
{
...
}
}

Answer 1

The easy way is to cast the id to integer, if the id is an integer that is:
$id = (int)$_GET['id'];
But it's strongly recomended to use pdo or mysqli with prepared statements:
http://php.net/manual/en/book.pdo.php
http://php.net/manual/en/book.mysqli.php

Answer 2

You can do a redirect whenever mysql_fetch_row() don't return anything (i.e. because there is no id 89)
Something like:
if (!$row = mysql_fetch_row($result)) {
header(Your error page);
}

Answer 3

Warning: mysql_fetch_row() expects parameter 1 to be resource
This means the the $result = mysql_query(....); call you made before the mysql_fetch_row() failed and resulted FALSE instead of a Resource ( i.e. a handle to the query result );
Look at the query, post it if possible, that is where your problem is.

Answer 4

Your code assumes that the query was successful without checking. For debugging purposes, add an 'or die(mysql_error())' line to the end of the mysql_query() statement.
$query = mysql_query("SELECT * FROM news WHERE id=".$_GET['id']."") or die( mysql_query() );
For more robust error handling in production applications, check the value of $query and log an error if it is false.
if (false === $query ) {
// Log error and/or notify an administrator
}
else {
while($news = mysql_fetch_row($query)) ...
As pointed out in other answers, you should ensure that the value of the id parameter is an integer since your query assumes that it will be. You can do this by casting:
(int)$_GET['id']
or via more robust type checking
if ( !is_numeric( $_GET['id'] ) ) {
// Take appropriate action
}
else {
// Create and execute the query