Now i discuss about SQL injection-- Note: #1. For guys who don't have any introduction to sql don't read this blog and go to this link . #2. If you have a little intro to sql then this blog is for you . SQL Injection is Nothing, It is just a tricky queries..... Explaination With Examples- Suppose i have a database named 'examples' and it has a table named 'user', witch have two column with name 'user' and 'password'. below pic will describe this... Now i integrate this with php to query in this table- $value=$_POST['input_form_value']; //this is input value from a form $sql='SELECT password FROM user WHERE user='$value'"; after this i query like this- $result=mysqli_query($myslqli_info,$sql); NOW TRICKY QUERY - In input form just input ' OR 1=1--' this will blow the query and gives you any password that you want. HOW IT WORKS-- our sql statements was- $sql='SELECT pa...