To "echo" in the context I was using it, just means to print (using the echo or print function) the variables to the screen so you can check to see if the contents are as you expected. This is a common debugging technique, and can help you identify problems in the assignment of values to your variables.
Information on the print and echo functions can be found in the PHP manual (check here for "print" and check here for "echo").
Note: Normally I would link you to http://www.php.net , but it is not responding to requests as I type this. The manual is the same on both sites, though there are more "comments" on the php.net site).
Essentially, you can display the contents of a variable at various stages in your program by inserting these functions into your code at various places:
print $variable; or
just put one of these into your code where you want to determine the contents of the variable, and as the code runs, you will be able to see what the variable holds at that point in the program's execution. Once you are satisfied the values are as expected, you can just delete them. If you find the variables do not contain what you expect, you can work on your code until they do, using these "check" outputs to verify how your code is impacting the variables.