a few questions

gkman · February 9th, 2012, 02:18 PM

I have reached to chapter 8 in the book with a few small questions I have.

1) the $_POST array- does it delete itself after the script on the page is executed? (I have been thinking that if i have 2 different forms in my site both share some fields in common and in one point I filled in one of the forms and after a of bit of browsing fill in the second form. will the second form processing script will use the first form input?)

2) I noticed as the book progresses the explanations are becoming less detailed (which is understandable on certain parts of the script that uses familiar code)
and some of the code is left unexplained (or not explained enough). this includes the code

Code:

header (âcontent-type: image/jpeg)

(what does it do? can I use the same concept for other file types?) and the imagecreatetruecolor() and imagecopyresample() functions (the last two where explained about what they do but not how to use them or their arguments ) in chapter 7. also the join() function that is (used in chapter 8 page 224) is not explained. this function I actually searched and found in the php documentation and in this place: http://www.w3schools.com/php/func_string_join.asp
and it seems you mixed between the two arguments of the function.

3) I saw many times in the book that when you make an insert query you place the query into a $result variable. I wanted to know if I have to that or I can just make the query

example:

Code:

 $query = âINSERT INTO images (image_caption, image_username, image_data) VALUES (âyadiâ, âyadiâ, âyadaâ)â;

// insted of $result = ..
$result = mysql_query($query, $db) or die(mysql_error($db);

// just simply .
mysql_query($query, $db) or die(mysql_error($db);

4) I don't know if you will cover this later in the book (I am right now in chapter 8) but how do I deal with empty fields in the data base or a query that returns nothing?

irProject · February 10th, 2012, 05:58 PM

Hi my friend!
the $_POST array refers to values that are submited to current page. so it would be destroyed after page execution.

Code:

<form name='myForm' action='destination.php' method='post'>
   firstname: <input type='text' name='firstname' /><br/>
   lastname: <input type='text' name='lastname' /><br/>
   <input type='hidden' name='someHidden' value='someValue' />
   
   <input type='submit' name='submit' value='submit the form' />
</form>

destination.php

Code:

if(isset($_POST["submit"])){
     $firstname = $_POST["firstname"];
     // ...
}

=================
you can also use combination of GET and POST methods:

Code:

<form name='myForm' action='destination.php?p=add' method='post'>
   firstname: <input type='text' name='firstname' /><br/>
   lastname: <input type='text' name='lastname' /><br/>
   <input type='hidden' name='someHidden' value='someValue' />
   
   <input type='submit' name='submit' value='submit the form' />
</form>

destination.php

Code:

$p = $_REQUEST["p"];
switch($p){
  case "add":
     $firstname = $_POST["firstname"];
     // ...
     // write insert statements here ...
     break;
   
  case "edit":
     $id = $_POST["id"]; // id may be a hidden field
     $firstname = $_POST["firstname"];
     // write update statements here ...
     break;
}

irProject · February 10th, 2012, 06:25 PM

Hi again.
this question should be detailed:

Code:

vardump($question); //!!!!!!

about 'content-type':
when a page is rendered, it should be returned to the user (browser). there are two types of data sent to browser: 1: headers, 2: content
header can contain some fields, such as 'content-type', cookie data, etc. header's data is processed by the browser. by default php sends 'content-type: text/html' header to the browser. if you use:

Code:

header ('content-type: text/plain');

the content of your page would not be processed as html, but plain text.
some times you need to send a special type of file to the browser (for download or other purposes); then you can use 'content-type: <mime-type>' header.
common used mime-types are :
* text/html
* text/plain
* image/jpeg
* application/octet-stream // can be widely used
* application/pdf

you can find a list of available mime-types in http://www.webmaster-toolkit.com/mime-types.shtml

I don't know php so I can't help about imagecreatetruecolor() and imagecopyresample() functions.

irProject · February 10th, 2012, 06:43 PM

There are simply four Data-Manipulation commands in Database Systems: SELECT, INSERT, UPDATE, DELETE

SELECT command returns a result set.
INSERT, UPDATE and DELETE commands return number of affected rows.

in many cases, the result of INSERT command may be ignored. so you can ignore the result by writing:

Code:

mysql_query($query, $db) or die(mysql_error($db);

or use result (maybe for 'multiple rows insertion') by writing:

Code:

$result = mysql_query($query, $db) or die(mysql_error($db);

in php (and common languages) you can avoid storing returned result of a function

$result = someFunction($a, $b);
or
someFunction($a, $b);