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SoCoder -> Blogs Home -> Blogs

 
Stealth
Created : 04 February 2011
 

PHP being weird!
So I was busy coding away at work and I ran in to the most weird PHP issue I've ever had.

So here was the problem from my perspective. I was creating a script that writes out records into a PDF. For some strange reason, the last two rows were identical. I scratched my head and thought maybe the database had duplicates. Nope. Maybe my query is wrong? Nope. Maybe I have some funky logic that is doing that. Sorta.

Like a lot of languages, PHP lets you assign a reference to a variable:



This causes some very interest problems when you reuse the reference in a foreach() loop:

(Please ignore the obvious way to simplify this code. It's just a very simple example.)


The reference will cause the pointer inside of $value to be carried over to the second foreach loop. This results in quirky problems.

The solution is pretty simple. Just unset $value:



It's not technically a bug so the PHP developers wont fix it. The expected behavior of the foreach() loop is to reset the pointer, so this issue will trip a lot of people up. It's not documented anywhere either.

 

Comments
Friday, 04 February 2011, 20:05
JL235
 		This is one of the reasons why you shouldn't use pointers because you get strange corner cases like this.
Saturday, 05 February 2011, 02:43
Afr0
 		Why would you write records into a PDF? o_O
Saturday, 05 February 2011, 12:18
JL235
 		If you ever want to give someone a document (one for them to keep) then PDF is almost certainly the best format to use.

I imagine that's what Stealth is doing, generating a document for people to keep.
Sunday, 06 February 2011, 00:15
Stealth
 		Correct. These are end of the month statement records that businesses will want to keep copies of.
Sunday, 06 February 2011, 03:25
Afr0
 		If they wanna keep copies then those copies should be in a DB, not in a PDF.
Sunday, 06 February 2011, 04:44
Jayenkai
 		PDFs are how companies operate.
It's just the way it is.
Although we all know Fax machines are completely feckin' useless, they will still be used by 10,000,000,000 businesses each and every day.
A PDF is a software version of a fax, and will be inexplicably used until after we're all long and dead.

It's just the way it is.
No point in arguing about it.
Sunday, 06 February 2011, 07:51
JL235
Afr0 If they wanna keep copies then those copies should be in a DB, not in a PDF.
You can't e-mail someone a DB entry, or offer it as a download (well you can but it's not very user intuitive). You can with a PDF.
Sunday, 06 February 2011, 22:13
Stealth
 		It also could potentially be printed. So PDFs are a good choice.
Monday, 07 February 2011, 08:26
Evil Roy Ferguso
 		I think this is another good argument for lexical scope.