php notes 

1. since designed with unix systems in mind, most parts is case sensitive...especially the one related to variable 
   calling etx 
   
2. the difference between get and post is well known but one of the main advantages of the post method is 
   it can be used to send greater amount of information to be sent to the server. THERE IS A PHYSICAL LIMIT TO THE 
   amount you can transmit as part of the URL ...which is what the get method does ...so post is preferred or the only 
   option in cases where there is the textarea control etc...
   
3. one disadvantage of the post method is the pages cannot be properly bookmarked wheras those pages with get can as
   the query string etc are part of the URL
   
4. Aslo URL encoding is used in the case of post method to avoid ambiguities that might arise in complex data sending ...

5. Array indexes always start from 0

6. always make sure to use $_GET['quantity'] , $_POST['quantity'];; etc to get the variables ..likewise for the post ....this is not stated in the book
	perhaps that might be because the book is written for somebody testing the codes usinf their own system as the server
	
	
7. $capital=$_GET['Question1']; always copy the variable values that you get from the GET AND POST methods to a local 
	varialble that you declare in that specific file => reduces error a lot 
	
	
8. The syntax to read the values of a multiple list box which is declared as 

 is  (use get/posr)
 <SELECT NAME="EngineSize[]" MULTIPLE>
	<OPTION>1.0L</OPTION>
	<OPTION>1.4L</OPTION>
	<OPTION>1.6L</OPTION>
	<OPTION>2.0L</OPTION>
</SELECT>
 e.g. 
 $size1=$_GET['EngineSize'][0];
	$size2=$_GET['EngineSize'][1];
	$size3=$_GET['EngineSize'][2];
	$size4=$_GET['EngineSize'][3];
	
9. $capital=$_GET['Question1'];
echo "you selected the answer: $capital "; (**)
echo $capital;

  the above is exacly the same as 
  
  $capital=$_GET['Question1'];
echo "you selected the answer:".$capital; (*)
echo $capital; 

see the differnce is in the fact that in the second(*) we are using string concatentaion...in fact the parser takes this and 
first generates the same as in (**)


10.  HIDDEN FORM FIELDS  for persistence ->see after 21


11. see page 143 how to execute a malicious script through the input! interesting...also see how to stop
		
	especially the HTMLSpecialChars function
	
12. See the dynamic creation of form elements and data capturing using array of textbox etc
echo "<INPUT NAME=Child[] TYPE=TEXT>"; ....page 163 

13. WHENEVER THERE IS A NEED REFERENCE ARRAYS ON PAGE 167 ...see that in PHP, no allocation etc by the user...immediately the engine
	does it for you ...cool ...see the mentioned page...from page 167 to 189 a lot of array related stuff
	
14. In the php engine that I am using(.pa.msu.) there are some syntax differnces like 
	echo "<BR> <BR>".$_GET["Child"][$Count] cannot be written as echo "<BR> <BR> $_GET["Child[$Count]"]" as the book advocates.
	
15. in php, by value and by reference are there 
     example 
     function tax($salary)
     {
     $salary=$salary + ...
     }
     this is by value 
     function tax(& $salary) => this is by reference
     {
     $salary=$salary + ...
     }
     
     the trap when using by reference, just like c++ etc 
     e.g. echo (tax(2000)); => cannot be used for the by reference case 
     but rather use 
     $salary=2000;
     echo (tax(&$salary));=>correct
     
 16. Global and local variables 
 	variables inside a function => local just like other languages
 	
 	$GLOBALS["VariableName" ]=>This is to access the GLOBALS array ...
 	
17. Using the static key word to retain the values of local vars 
 	e.g. function number_hits()
 	     {
 	     	static $number=0;
 	     	return $number = $number + 1;
 	     }
 	     
 	     in the above, the first time the function is called, $number is initialized with 0...aftre that the first sentence is not 
 	     executed thereby retaining the previous value and one being added everytime it is called ..
 	     
18. see nesting of functions ...though not that useful
 function pension($Total)
 {
 	function tax($Salary)
 	{
 	return $Salary-10;
 	}
 	$Posttax=tax($Total);
 	return tax($Total)-(($Posttax/100)*3);
 
 }
 
 $Total=2500;
 echo (pension($Total));....actually when nesting PHP 4.0 outputs errors =>thus use nesting only for recusion...see page 216
 e.g. 
 function recursion ($val)
 {
 	if ($val<=1) 
 		return 1;
    else 
    	return $val*recursion($val-1)
    	
    	
19. include files 
  include("text.txt")...it will include the file at that particular points...text or html=>parsed...
  
20. see handling and avoiding error chapter 225-259
21. for comments use //

------------------see the program for e-mail checking using regular expression...it is cool------------
			Persistence 
		========================
		
1. do it urself persistence
		
  using Hidden => until one decides to commit the data stored in these variables to disk, the information stored in them exists
  only in the memory occupied by the Client's browser
  ....mostly used in continue...sign up etc multiple forms to pass info from 1->2->3...see page 263