Word Search PHP Tutorial

Hello,
I am trying to follow this tutorial on making a php word search and the code was provided by the book I am learning. The problem is when I generate word search it doesn't work. Can someone help me figure out what is going wrong?

HTML to input words into the word search
PHP for generating word search
Answer Key for word search PHP code

This is from the book code so I don't understand why its not work.

I appreciate anyone who can help this noob learning web programming (first time) some guidance.

thank you