"Warning: Invalid error type specified in ...\PHPWord.php on line 226" is thrown when the specified template file is not found

[ghost]

The problem is in the followed statement:
trigger_error('Template file '.$strFilename.' not found.', E_ERROR);

Due to http:https://php.net/manual/en/function.trigger-error.php:
"It only works with the E_USER family of constants, and will default to E_USER_NOTICE."

So, replacing E_ERROR with E_USER_ERROR helps.