This is an HTML issue with your code <https://stackoverflow.com/questions/44425858/the-character-encoding-of-the-html-document-was-not-declared>, and that error message is returned by your Browser. This is not an issue with Google. It is recommended to ensure you are correctly setting your charset as explain in w3schools <https://www.w3schools.com/html/html_charset.asp>:
<meta charset="UTF-8"> - Note that Google Groups is for general product discussions and is not for technical support. It is recommended to continue all further troubleshooting in your Stack Overflow <https://stackoverflow.com/questions/48584740/google-app-engine-php-dev-local-the-character-encoding-of-the-html-document-ha> post. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to firstname.lastname@example.org. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/9c24f9c6-934a-44ba-b117-357099baea9c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.