HTML : Beginner php 'Warning: Undefined array key'

HTML : Beginner php "Warning: Undefined array key"
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

As promised, I have a hidden feature that I want to share with you.
This is a YouTube's feature which works on Desktop.
First, Make sure this video is playing.
Next, enter the letters 'awesome' on your keyboard.
Your YouTube progress indicator will turn into a shimmering rainbow.

A little intro about me,
Hey, I am Delphi.
Allow me to provide support in answering your questions.
HTML : Beginner php "Warning: Undefined array key"
Let me know if you have more specific queries by commenting or chatting with me.
We welcome your thoughts and feedback, so please comment below with your answer or insights to the answer.
Your answer will be recognized and valued, and I will 'heart' it to show my appreciation.
php HTML "Warning: key" Beginner Undefined array :