How can I prevent SQL injection in PHP?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to SQL injection, like in the following example:

$unsafe_variable = $_POST['user_input']; 
mysql_query(“INSERT INTO table (column) VALUES (‘$unsafe_variable’)”);

That’s because the user can input something like value’); DROP TABLE table;–, and the query becomes:

INSERT INTO table (column) VALUES(‘value’); DROP TABLE table;–')

What can be done to prevent this from happening?

#mysql #cakephp