Type cast if possible your parameters. But it’s only working on simple types like int, bool and float.

$unsafe_variable = $_POST['user_id'];

$safe_variable = (int)$unsafe_variable ;

mysql_query("INSERT INTO table (column) VALUES ('" . $safe_variable . "')");

NOTE: This answer was originally posted at StackOverflow.com by devOp

In my opinion, the best way to generally prevent SQL injection in your PHP app (or any web app, for that matter) is to think about your application’s architecture. If the only way to protect against SQL injection is to remember to use a special method or function that does The Right Thing every time you talk to the database, you are doing it wrong. That way, it’s just a matter of time until you forget to correctly format your query at some point in your code.

Adopting the MVC pattern and a framework like CakePHP or CodeIgniter is probably the right way to go: Common tasks like creating secure database queries have been solved and centrally implemented in such frameworks. They help you to organize your web app in a sensible way and make you think more about loading and saving objects than about securely constructing single SQL queries.

NOTE: This answer was originally posted at StackOverflow.com by Johannes Fahrenkrug

If you want to take advantage of cache engines like redis or memcache maybe DALMP could be a choice, it uses pure mysqli, check this: http://www.dalmp.com/PExecute

Also you can ‘prepare’ your arguments before preparing your query so that you can build dynamic queries and at the end have a full prepared statements query. http://www.dalmp.com/Prepare

NOTE: This answer was originally posted at StackOverflow.com by nbari

The right way to prevent SQL injection is by using parameterized queries. This means defining the SQL code that is to be executed with placeholders for parameter values, programmatically adding the parameter values, then executing the query. Doing this allows the server to create an execution plan for the query, which prevents any “injected” SQL from being executed. An example will help in explaining this. Let’s use the same script, but I’ll define the SQL query with parameter placeholders:

$sql = "SELECT * FROM Tbl WHERE Username = ? and Password = ?";

Now, I’ll define an array that holds the parameter values:

$params = array($_POST['Username’], $_POST['Password’]);

When I execute the query, I pass the $params array as an argument:

$stmt = sqlsrv_query($conn, $sql, $params);

NOTE: This answer was originally posted at StackOverflow.com by Nirav Ranpara

As you can see, people suggest you to use prepared statements at the most. Its not wrong, but when your query is executed just once per process, there would be a slightly performance penalty. I was facing this issue but I think i solved it very very sophisticated way – the way hackers use to avoid using quotes. I use it to prevent all possible sql injection attacks.

My approach:

• if you are expect input to be integer make sure its really integer. In variable-type language like is php is this very important. You can use for example very simple but powerful solution: sprintf("SELECT 1,2,3 FROM table WHERE 4 = %u", $input);
• if you are except anything else from integer hex it. If you hex it, you will perfectly escape all input. In C/C++ there’s a function called mysql_hex_string(), in php use bin2hex(). Dont worry about that the escaped string will have 2x size of its original length because even if you use mysql_real_escape_string or bin2hex, php have to allocate same capacity ((2*input_length)+1). This hex method is often used when you transfer binary data but I see no reason why not use it to all data to prevent sql injection attacks. Note that you have to prepend 0x or use mysql function UNHEX.

So for example query:

SELECT password FROM users WHERE name = 'root'

Will become:

SELECT password FROM users WHERE name = 0x726f6f74

Perfect escape. No way to inject.

Note that this hex is often used as a sql injection attacks where integers are just like strings and escaped just with mysql_real_escape_string, then you can avoid of use of quotes. For example if you just do something like this:

"SELECT title FROM article WHERE id = " . mysql_real_escape_string($_GET["id"])

attack will very easy inject you. Consider the following injected code returned from your script:

SELECT ... WHERE id = -1 union all select table_name from information_schema.tables

SELECT ... WHERE id = -1 union all select table_name from information_schema.tables where table_name = 0x61727469636c65

But if would the coder of injectable site hex it, no injection would be possible:

SELECT ... WHERE id = 0x2d3120756e696f6e20616c6c2073656c656374207461626c655f6e616d652066726f6d20696e666f726d6174696f6e5f736368656d612e7461626c6573207768657265207461626c65203d2030783631373237343639363336633635

NOTE: This answer was originally posted at StackOverflow.com by Zaffy

For those unsure of how to use PDO (coming from the mysql_ functions), I made a very, very simple PDO wrapper that is a single file. It exists to show how easy it is to do all the common things applications need done. Works with PostgreSQL, MySQL, and SQLite.

Basically, read it while you read the manual to see how to put the PDO functions to use in real life to make it simple to store and retrieve values in the format you want.

I want a single column

$count = DB::column('SELECT COUNT(*) FROM `user`);

I want an array(key => value) results (i.e. for making a selectbox)

$pairs = DB::pairs('SELECT `id`, `username` FROM `user`);

I want a single row result

$user = DB::row('SELECT * FROM `user` WHERE `id` = ?', array($user_id));

I want an array of results

$banned_users = DB::fetch('SELECT * FROM `user` WHERE `banned` = ?', array(TRUE));

NOTE: This answer was originally posted at StackOverflow.com by Xeoncross

I use three different ways to prevent my web application from being vulnerable to SQL injection.

1. Use of mysql_real_escape_string(), which is a pre-defined function in PHP, and this code add backslashes to the following characters: \x00, \n, \r, \, ', " and \x1a. Pass the input values as parameters to minimize the chance of SQL injection.

2. Use of MySQLi.

3. The most advanced way is to use PDOs.

I hope this will help you.

NOTE: This answer was originally posted at StackOverflow.com by Soumalya Banerjee

There are many ways of preventing SQL injections and other SQL hacks. You can easily find it on the Internet (Google Search). Of course PDO is one of the good solution. But I would like to suggest you some good links prevention from SQL Injection.

What is SQL injection and how to prevent

PHP manual for SQL injection

Microsoft explanation of SQL injection and prevention in PHP

and some other like Preventing SQL injection with MySQL and PHP

Now, why you do you need to prevent your query from SQL injection?

I would like to let you know: Why do we try for preventing SQL injection with a short example below:

Query for login authentication match:

$query="select * from users where email='".$_POST['email']."' and password='".$_POST['password']."' ";

Now, if someone (a hacker) puts

$_POST['email']= admin@emali.com' OR '1=1

and password anything….

The query will be parsed in the system only upto:

$query="select * from users where email='admin@emali.com' OR '1=1';

The other part will be discarded. So, what will happen? A non-authorized user (hacker) will be able to login as admin without having his password. Now, he can do anything what admin/email person can do. See, it’s very dangerous if SQL injection is not prevented.

NOTE: This answer was originally posted at StackOverflow.com by Manish Shrivastava

Why are you all reinventing the wheel? A simple way to develop is to use some stable and reliable framework such as Joomla, Drupal or ZendFramework. The choice will rely on your needs and only you can select the appropriate one. If you just start using PHP, maybe it’s more difficult to choose because you need to have some basic knowledge about design patterns…but if you are experimented developer, you should already know that!

NOTE: This answer was originally posted at StackOverflow.com by Yoong Kim

Using this PHP function mysql_escape_string() you can get a good prevention in a fast way.

For example:

SELECT * FROM users WHERE name = '".mysql_escape_string($name_from_html_form)."'

mysql_escape_string — Escapes a string for use in a mysql_query

For more prevention you can add at the end …

wHERE 1=1   or  LIMIT 1

Finally you get:

SELECT * FROM users WHERE name = '".mysql_escape_string($name_from_html_form)."' LIMIT 1

NOTE: This answer was originally posted at StackOverflow.com by Nicolas Finelli

Parameterized query AND input validation is the way to go. There is many scenarios under which SQL injection may occur, even though mysql_real_escape_string() has been used.

Those examples are vulnerable to SQL injection :

$offset = isset($_GET['o']) ? $_GET['o'] : 0;
$offset = mysql_real_escape_string($offset);
RunQuery("SELECT userid, username FROM sql_injection_test LIMIT $offset, 10");

or

$order = isset($_GET['o']) ? $_GET['o'] : 'userid';
$order = mysql_real_escape_string($order);
RunQuery("SELECT userid, username FROM sql_injection_test ORDER BY `$order`");

In both case you can’t use ‘ to protect the encapsulation.

source : The Unexpected SQL Injection (When Escaping Is Not Enough)

NOTE: This answer was originally posted at StackOverflow.com by Cedric

Injection Prevention – mysql_real_escape_string()

PHP has a specially-made function to prevent these attacks. All you need to do is use the mouthful of a function mysql_real_escape_string.

What mysql_real_escape_string does is take a string that is going to be used in a MySQL query and return the same string with all SQL Injection attempts safely escaped. Basically, it will replace those troublesome quotes(‘) a user might enter with a MySQL-safe substitute, an escaped quote \’.

/NOTE: you must be connected to the database to use this function!
// connect to MySQL

$name_bad = "' OR 1'"; 

$name_bad = mysql_real_escape_string($name_bad);

$query_bad = "SELECT * FROM customers WHERE username = '$name_bad'";
echo "Escaped Bad Injection: <br />" . $query_bad . "<br />";


$name_evil = "'; DELETE FROM customers WHERE 1 or username = '"; 

$name_evil = mysql_real_escape_string($name_evil);

$query_evil = "SELECT * FROM customers WHERE username = '$name_evil'";
echo "Escaped Evil Injection: <br />" . $query_evil;

you can find more detail here

http://www.tizag.com/mysqlTutorial/mysql-php-sql-injection.php

NOTE: This answer was originally posted at StackOverflow.com by rahularyansharma

Every answer here covers only part of the problem.
In fact, there are four different query parts which we can add to it dynamically:

• a string
• a number
• an identifier
• a syntax keyword.

and prepared statements covers only 2 of them

But sometimes we have to make our query even more dynamic, adding operators or identifiers as well.
So, we will need different protection techniques.

In general, such a protection approach is based on whitelisting.
In this case every dynamic parameter should be hardcoded in your script and chosen from that set.
For example, to do dynamic ordering:

$orders  = array("name","price","qty"); //field names
$key     = array_search($_GET['sort'],$orders)); // see if we have such a name
$orderby = $orders[$key]; //if not, first one will be set automatically. smart enuf :)
$query   = "SELECT * FROM `table` ORDER BY $orderby"; //value is safe

However, there is another way to secure identifiers – escaping. As long as you have an identifier quoted, you can escape backticks inside by doubling them.

As a further step we can borrow a truly brilliant idea of using some placeholder (a proxy to represent the actual value in the query) from the prepared statements and invent a placeholder of another type – an identifier placeholder.

So, to make long story short: it’s a placeholder, not prepared statement can be considered as a silver bullet.

So, a general recommendation may be phrased as
As long as you are adding dynamic parts to the query using placeholders (and these placeholders properly processed of course), you can be sure that your query is safe.

Still there is an issue with SQL syntax keywords (such as AND, DESC and such) but whitelisting seems the only approach in this case.

NOTE: This answer was originally posted at StackOverflow.com by Your Common Sense