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With GetSimple 3.1, plugins will check “home” periodically to see if there is an update available within the Extend repository. The steps needed to ensure your plugin is compatible are minimal:
The zip file you upload into Extend should be in this structure:
yourplugin.zip /yourplugin.php [this should be a unique across all plugins] /yourplugin/ [any folder(s) that your plugin may utilize]