PHP 7.0 Compatibility

Hi!

I’ve tested all my plugins with this PHP linter:
https://wordpress.org/plugins/php-compatibility-checker/

Unfortunately I found a problem with your plugin:

FILE: /srv/www/vhosts/nessuna.ch/httpdocs/nessuna/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/lib/dompdf/include/page_cache.cls.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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40 | WARNING | Method name “Page_Cache::__query” is discouraged; PHP has reserved all method names with a double underscore prefix for future use
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Would be great if you can fix this!

Regards,
Demian