php_sqli is definitely to be preferred over php_sql.
This is from the PHP manual, intro section to php_mysqli:
The mysqli extension allows you to access the functionality provided by MySQL 4.1 and above. More information about the MySQL Database server can be found at » http:
An overview of software available for using MySQL from PHP can be found at Overview
Documentation for MySQL can be found at » http:
Parts of this documentation included from MySQL manual with permissions of MySQL AB.
AFAIK, php_pdo is simply an abstraction layer to provide db-independent access methods, so if you're sticking with mysql, it doesn't buy you much.
For what I think you're trying to do, have a look at the MySQLi_STMT class in the PHP manual.
Cheers,
Peter