asked on

Code snippet driving me mad....

HI all,
I have a small bit of PHP code that is driving me mad.

$parent_id is obtained from a value in a database.
The problem is that even when the value is 0 in the database the script doesnt seem to detect it. Ive echoed out parent_id so I know its 0. Ive tried intval($parent_id) but that doesnt seem to work.

If I put $parent_id=0; it works fine. Anyone have an idea of what Im doing wrong?

Here is the code snippet.

            if ($parent_id===0) {
                  return $title;
            } else {
                  dothis($parent_id);
            }

Loganathan Natarajan

please ensure $parent_id has value 0 or empty.. only then the condition will work properly.

Loganathan Natarajan

You may use trim () or empty() function to check the value then you can use isset()

ienaxxx

... If I put $parent_id=0; it works fine. Anyone have an idea of what Im doing wrong?
it's cause it SETS the value to 0 while checking the ASSIGNMENT operations with "=" ends correctly.

Are you sure the $parent_id is 0 and not, for example, an array?

Try to echo $parent_id right before the check.
Try to print_r($parent_id).

What is the result?

Chris Harte

Using triple === is safe type checking. That means the value read from the database has to be an int of value zero, which is different from a char '0'.

Try it with double == and see if that works

Kim Walker

Interesting. According to PHP documentation, intval returns zero on failure. And any string beginning with a zero is treated as an octal number so I guess intval would shift to octal and return a null value for a single zero. But the documentation doesn't mention how it returns a true value of zero even if the string were "00".

Why do you need to convert it? Why not just use $parent_id === '0'?

Hugh McCurdy

I agree with MunterMan (before I read his post).

Why are you using === instead of ==? If there isn't a very good reason, please try ==. (Even if there's a good read, try == and see if the code works and then we can discuss the reason.)

ASKER CERTIFIED SOLUTION

Ray Paseur

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

Hugh McCurdy

Ray, that's a good point about the db returning strings. Pretty concisely identifies the problem.

Hugh

fox_statton

ASKER

I just did the var dump and its showing int(0)

tried changing == to === but still not working.

fox_statton

ASKER

okl, so ive dug a little deeper and found that the match is fine.

It appears for some reason that "return $title" is not returning the variable title

So when I call the function the page using

$sys=dothis($id);
echo $sys;

it shows nothing.

Ray Paseur

@fox_statton: Do you know the story about the blind men and the elephant? We are looking at fragments of information here, and "return $title" is not part of the question. There could be any number of things wrong. Maybe you should give us a more comprehensive overview of what you're trying to achieve. Post the code that is failing and we might be able to tell you how to go about diagnosing and correcting the errors. Thanks and regards, ~Ray

Hugh McCurdy

Is there anything in $title?

var_dump ( $title );

fox_statton

ASKER

yes, title is showing string(25)

fox_statton

ASKER

This is what my function looks like:

function find_top_parent($id) {
	$query="SELECT from database etc";

	$result=mysql_query($query);
	$num=mysql_numrows($result); 
	$i=0;

	while ($i < $num) {

		 $title=mysql_result($result,$i,"title");
		 $parent_id=intval(mysql_result($result,$i,"parent_id"));


		if ($parent_id==0) {
		echo "MATCH FOUND $title";
			return $title;
		} else {
		echo "NO MATCH FOUND";
			find_top_parent($parent_id);
		}

		++$i;
	}

}

Open in new window

fox_statton

ASKER

Its a recusive function that Im using to keep searching until it finds parent_id=0

then its supposed to return the title of item with parent_id=0

Ray Paseur

$query="SELECT from database etc";

A statement like this is virtually useless if you want help in debugging. We really need to see accurate information.

A way to make the query and find the title and parent_id might be something like this code snippet (untested, because I do not have your data base). I cannot see how you use the $id argument, but maybe you can provide some additional information about that.

function find_top_parent($id) 
{
    $query  = "SELECT parent_id, title FROM mytable WHERE (some clause) ORDER BY parent_id DESC";
    $result = mysql_query($query);
    if (!$result) die("$query" . mysql_error());
    while ($row = mysql_fetch_assoc($result))
    {
        if ($row["parent_id"] == 0)
        {
            return $row["title"];
        }
    }
}

Open in new window

Kim Walker

I may be stating the obvious, but why aren't you letting MySQL do the work and just select the record with parent_id 0?

SELECT * FROM table WHERE parent_id=0

Open in new window

Then you wouldn't need to find it in PHP which is a lot of unnecessary work.

Ray Paseur

@xmediaman: If all the SELECT queries go to the same table you may have found the magical answer! And actually, you would only need to SELECT title from that table.

;-)

~Ray

fox_statton

ASKER

Ray Paseur

And this is in one table? Is this by any chance a school assignment?

fox_statton

ASKER

Yep, its in one table. Nope not a school assigment its for a system I built a long time ago, Im sure I did something similar and it worked, but not sure why his code isnt.

Ray Paseur

OK, maybe we are making progress. Can you please post the CREATE TABLE statement and tell us how many rows are in the table. Also please tell us how many tree structures are embedded within the rows. Thanks, ~Ray

fox_statton

ASKER

Hi guys,
ok managed to fix it. phew!

It was all down to the recurvie function, had to restructure it, as the variable was not being preserved. I did something similar years ago using arrays, but have obvioulsy lost some of those skillz!

Thanks for all the help.