Fatal error: Class 'WP_Theme' not found in wp-includes/theme.php on line 106

Fatal error in the output generally indicates either your theme doesn’t like your version of WordPress, you have a plugin that doesn’t like your version of WordPress, or you have an incomplete install/upgrade.

so,try:

–resetting the plugins folder by FTP or phpMyAdmin.
– it could be a problem with the theme. Momentarily, try switching to the default twentyeleven theme via FTP by renaming your current theme to rule out any theme specific issue.

i tried the plugins folder… no change..

how do i get my theme changed via ftp?

upon further review of deprecated.php line 30101 looks like this:

3101 $theme = new WP_Theme( basename( dirname( $theme_file ) ), dirname( dirname( $theme_file ) ) );
3102
3103 $theme_data = array(
3104 ‘Name’ => $theme->get(‘Name’),
3105 ‘URI’ => $theme->display(‘ThemeURI’, true, false),
3106 ‘Description’ => $theme->display(‘Description’, true, false),
3107 ‘Author’ => $theme->display(‘Author’, true, false),
3108 ‘AuthorURI’ => $theme->display(‘AuthorURI’, true, false),
3109 ‘Version’ => $theme->get(‘Version’),
3110 ‘Template’ => $theme->get(‘Template’),
3111 ‘Status’ => $theme->get(‘Status’),
3112 ‘Tags’ => $theme->get(‘Tags’),
3113 ‘Title’ => $theme->get(‘Name’),
3114 ‘AuthorName’ => $theme->get(‘Author’),
3115 );
3116
3117 foreach ( apply_filters( ‘extra_theme_headers’, array() ) as $extra_header ) {
3118 if ( ! isset( $theme_data[ $extra_header ] ) )
3119 $theme_data[ $extra_header ] = $theme->get( $extra_header );
3120 }
3121
3122 return $theme_data;
3123 }
3124
3125 /**

how do i get my theme changed via ftp?

If you don’t have access to your admin area, you can switch to the default theme by renaming your current theme’s folder in wp-content/themes via FTP or SFTP or whatever file management application your host provides.

thats pretty vague… change it to what?

i already tried that and it didnt work.

If you follow t-p’s instructions, the default WordPress theme will be automatically activated. Also try re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.

been doing this with no success. i am running out of options i think.

I got it updated finally , but still have a white screen for admin panel.

-Usually when this happens there is an issue with your themes functions.php file. Try reverting the to defulat theme and see if that works.

-if you would try the functions file again, make sure no “returns” or blank spaces follow the closing php tag. thats been my experience anyway. good luck