Simple Variable problem

[jaZon]

I feel really dumb for not being able to figure this out....

So anyway, I have a variable called

$serial

. It will always hold a numerical value....

NOW, I have an array that drops in the values, so instead of having:

http://www.whatever.com/test/test.php?$serial=0

it comes out

http://www.whatever.com/test/test.php?002010=0

Then I have a little if statement:

if($serial == "0"){
	unset($cart[$serial]);
}

And well, that doesn't work.

[drew010]

its probably not working because you can't perform an assignment inside a string.
while variables are parsed inside " marks, you cant actually run code.

what this means...

$value = 0;

echo "http://www.site.com/file.php?$value=10";

will evaluate to
http://www.site.com/file.php?0=10
which is what you are getting

if you want to assign to $serial, it cannot be inside quotes, it should be either on its own line, or written like
"http://www.whatever.com/test/test.php?" . $serial=0;

its similar to the fact that
echo "2 + 2";
will print 2 + 2
while
echo 2 + 2;
will print 4

hope that cleared it up for you.

[jaZon]

Ok, I get what you're saying, but I didn't properly explain the situation.

I'm using sessions to store an array....kind of a very simple shopping cart, I suppose.

The array holds the value of $serial and a quantity - I'm using this statement:

foreach($cart as $serial => $qty){

if($$serial == "0"){
	unset($cart[$serial]);
}

$url = "testbed.php?$serial=0";

mysql_connect ('host', 'blah', 'blah');
mysql_select_db ('database');
$query = "SELECT * FROM hmedical_oxygen WHERE oxygen_status=1 AND oxygen_serial = $serial";

$result = mysql_query("$query");
while ($row = mysql_fetch_array($result)){
	echo("<tr><td><a href=$url>$row[oxygen_serial]</a></td><td>$row[oxygen_lot]</td><td>$row[oxygen_tank] - $qty</td></tr>");
}
}

Now, I realize that that is convoluted. What I'm trying to do is have the person click on the link and have that value in the array be deleted.

And yes, I've kind of pieced this together from reading a book(which is horrible) and my own randomness so there's no wonder it doesn't work.

[drew010]

ok i see now...

when you pass variables in the query string, you dont include the $ sign. thats only for code.

what you will really want to do is
$url = "testbed.php?serial=0";

now when testbed.php is called up, it receives the serial=0 from the query string, and assigns it to $GET['serial'] for you to use in code. if register_globals is off you will have it available as $serial and $GET['serial'].
a little unrelated to the post, its advised to use $_GET['serial'] for security and portability.

but anyway, once you run the script you can check the query string value...

if ($_GET['serial'] == 0) {
  unset($cart['serial']);
}

[jaZon]

🙁 still nothing - I've tried every combo I can - I really despise array's😕 😕

[drew010]

yeah i think i mislead you from the beginning, i see what you are trying to do now.
you actually want the numeric serial in the query string so you can unset it from the array because the serial itself is an index.

try this and see if it works...

foreach($_GET as $index => $val) {
  if ($val == 0) @unset($cart[$index]);
}

this way, if you put
testbed.php?00556=0
it checks first for the value of 0, if it is zero it does unset($cart[$index]) which in this case is $cart[00556].

[jaZon]

Ok, this is what the book has word for word

On one page in a form there is the following input:

echo "input type = text name = \"$isbn\" value = $qty size = 3>";

On the form post page:

<?

if($save){
	foreach($cart as $isbn => $qty){
		if($$isbn=="0")
			unset($cart[$isbn]);
		else
			$cart[$isbn] = $$isbn;
	}
}

I'm trying to do the exact same thing...just without the form.

[drew010]

try what i put above, and see if that works out.

[jaZon]

that last one has definitely helped - it's showing another weird problem, but let me play around with it for a few minutes.

Thanks!

[jaZon]

Ok, another question (Sorry for so many!)

Why use:

foreach($_GET as $index => $val) { 
  if ($val == 0) @unset($cart[$index]); 
}

instead of

foreach($cart as $serial => $qty){
 if ($qty == 0) @unset($cart[$index]);
}

Besides the obvious fact that the latter doesn't work, lol.

Also, should that @ be there? I removed it because it returned an error.

[drew010]

the reason i am using the query string to check values is mostly for efficiency. imagine if the cart has 50-60 items in the array, its a lot more time consuming to check 50-60 items for a query string value instead of checking maybe 1 or 2 actually passed via query string.

also it enables you to put that code on any page without worrying about indexing errors or what variables are passed. if there is nothing in get, it simply doesnt execute at all.

and as for the @, i guess im still thinking in php3, unset used to return a value and print errors if you unset an inexistant index, i just checked and remembered thats not the case, so yes you were smart to remove it.

but the @ is the error supression operator. if you have
$arr = array("hello");
and you try
echo $arr[999];
it will print an error about an undefined index on your webpage which is very bad in a live environment, so putting the @ in front tells php not to print the errors of the statement to the screen.

[jaZon]

Oh ok - That makes sense

The weird error I told you about is now when I click the link, the item disappears....exactly like I wanted. But then if I click another item....it takes that item away and replaces it with the last one that was supposedly taken off....

This is really giving me a headache - Any suggestions on DECENT books? ha

[drew010]

the book i used was an old version of this
the authors presented some nice clean sample code and explained the concepts well i thought.
after that most of my knowledge came from writing small scripts for myself. but the book was extremely helpful.
and of course the greatest resource, www.php.net/manual/en lots of great code and samples in there.

[jaZon]

thanks 🙂

i'll probably look for it tonight

in the meantime i'll be trying to figure out why these variables seem to only be "unsetting" until the next link is clicked