Auto increment in phpmyadmin
Solution 1:
There are possible steps to enable auto increment for a column. I guess the phpMyAdmin version is 3.5.5 but not sure.
Click on Table > Structure tab > Under Action
Click Primary (set as primary),
click on Change on the pop-up window, scroll left and check A_I. Also make sure you have selected None for Default
Solution 2:
In phpMyAdmin, navigate to the table in question and click the "Operations" tab. On the left under Table Options you will be allowed to set the current AUTO_INCREMENT value.