If you try to install ConvertPlug on servers running outdated PHP version, you might see an error like this –
Plugin could not be activated because it triggered a fatal error. Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM in /wp-content/plugins/convertplug/framework/Smile_Framework.php on line 73
Fatal error: Using $this when not in object context in /(...)/convertplug/admin/contacts/views/cp-paginator.php on line 70
If your server is running outdated PHP, this error is common as they uses double colon ( :: ) for accessing static object. WordPress needs PHP 5.6 or greater version installed on the server as specified here.
Please contact your Web Host for help and ask them to update PHP, especially because 5.4 has come to “End Of Life”.