Sometimes when editing .php files you will make a mistake and end up breaking your theme or sometimes you might upload a theme that is old and out of date or is just too problematic and it needs to be switched back to the twenty ten default theme. Here is an easy way to switch to the twenty ten default theme using PHPMyAdmin.
Second– Select the database where your WordPress is stored.
Third– Select the ‘wp_options’ table from the menu on the left.
Forth– Select page 2 from the tables header or footer:
Fifth– Now you’ll need to edit the ‘template’ and ‘stylesheet’ tables and put in the word “twentyten”, or any other theme you want. Press “Go” when you are done.