How can I demonstrate themes well?

Use a multisite installation. Let the main site be your announcement page and at least on sub-site the theme demo site. Then you can use special content like WP Test on that site. Some themes might require special content, like a shop theme that needs products. You can use another, separate sub-site for these themes.

Trouble creating custom sanitization function when uploading video files

validate_file doesn’t quite work the way you’re expecting it to – it checks if $file is in the allowed files array, not just its extension/mime type. You’re looking for wp_check_filetype. However, all that ultimately does is check the extension (i.e. it doesn’t read the headers of the file/ascertain the mime type otherwise). Unless you implement … Read more

How to install wordpress theme’s plug-ins?

It sounds like you are trying to upload archive files to the plugin directory. You can’t do that. You need to upload the original source files. Unzip or unrar the plugins (s)FTP the decompressed files to wp-content/plugins Activate the plugins from the backend control panel That should be all you need to do. Some of … Read more

Theme specific plugin, how?

You can ask for the activation of the theme. You can get the value of the options values templateand stylesheet. The stylesheet get the active style, a benefit if the user use an child theme. As example if ( ‘my_theme’ === get_option( ‘stylesheet’ ) ) …. Also you can use the hooks for template and … Read more