orphan.html

     This file has a form in it but it doesn't do anything...
     Since it has no php in it, no need to save with .php file extension




babyForm.html   mother.php

     The babyForm is 'functional' in that it calls it's mother...to handle things,(-:
     Since baby has no php in it, no need to save with .php file extension
     But mother is all about php and must be!

     Your author uses this condition in a lot of if-stmt's: 
             isset(  $_POST['key']  )  
        
     
 
        Ideally, we can read through the online documentation of EVERY function 
        we are using and depending on:
                  isset()
        and anything similiar...
                  empty()
                  is_null() 
          
                  var_dump() displays info about type & value; often useful for debugging PHP code

        
Here's a HUMAN-READABLE summary I've generated(on hive),(-:
                  table summary (local mirror) color-coded version

                    Pertinent info...   TIAS!!!
                          A variable is NULL if it has no value, and points to nowhere in memory.
                          empty() is more a literal meaning of empty, e.g. the string "" is empty, but is not NULL. 

                          What happens if a form field is left blank?  ie, "" the empty string?
      

AdultForm.php

     This is a more sophisticated construct similar to the ones in your book
     where the submits go to ... the EXACT SAME FILE