how to save a website from sql injections

 
 
 
 
 
which of the following code snippets best protects a system from sql injections?
1.sql_real_escape_storng()
2.mysql_real_escape_string()
3.mysql_real_escape()
4.mysql_not_real_delete_string()
the right answer is :
2(mysql_real_escape_string())