Connecting to Gmail IMAP PHP "Couldn't open stream"

You need port 993, the SSL IMAP port.

Port 995 is the SSL POP3 port.

I think Gmail's IMAP can only be accessed on port 993.

$hostname = "{imap.gmail.com:993/imap/ssl/novalidate-cert}";

I had the same error and found a different solution. I have added debug info into host:

"{imap.gmail.com:993/debug/imap/ssl/novalidate-cert}INBOX"; 

When I read php error log, I found

Unknown: [ALERT] Please log in via your web browser: https://support.google.com/mail/accounts/answer/78754 (Failure) (errflg=1) in Unknown on line 0

Open link, and follow instructions. Search for

Your app might not support the latest security standards. Try changing a few settings to allow less secure apps access to your account.

Click on link and enable less secure app access.

Then it works for me.