what is difference between sql & sqli??

Answer 1

“mysqli” extension is an improvement over the old “mysql” extension. In fact, the “i” in mysqli stands for “improved”.

mysqli was developed to take advantage of the new features available in MySQL since version 4.1.3. Also, you can use it since PHP 5. So, if you code with PHP5 with a newer version of MySQL, it’s strongly recommended for you to use the extension “mysqli” over “mysql”.

Answer 2

Or, talking about SQL as plain, you may say that SQLi stands for SQL injection, but we are getting into illegalities.