$new_sql = "select MAX(id) from reviews";
$get_new_sql= mysql_query($new_sql) or die(mysql_error());
$new_id = mysql_result($get_new_sql,"id");  
 
 
<?php
$link = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$link) {
   die('Could not connect: ' . mysql_error());
}
mysql_select_db('mydb');
 
mysql_query("INSERT INTO mytable (product) values ('kossu')");
printf("Last inserted record has id %d\n", mysql_insert_id());
?>