NULL or "" ?

medlington · February 5 '10, 07:19 AM (#1)

Hi,

I've learned PHP myself and as such have my own way of doing things.

When Ive been declaring a variable as nothing I've just been doing something like this:

PHP Code:


			
$variable = "";

Recently I came across the NULL and have realised I could declare the variable like this:

PHP Code:


			
$variable = NULL;

Whats the difference, will I get problems doing it one way over the other?

**mlseim** · February 5 '10, 09:39 AM (#2)

This explains it better than I can:
http://www.devshed.com/c/a/MySQL/Nul...Empty-Strings/

I never use NULL ...
I do it the way you have done it ... $variable = "";

To me, it just seems easiest, and I always know which way it is.
But there is probably a valid purpose for NULL.
This is also related to "isset". It can become an issue for the
way PHP processes form checkboxes.

medlington · February 5 '10, 09:52 AM (#3)

Thanks mate,

Nice to get some clarification. Il keep doing it the way I have been

smoseley · February 5 '10, 10:36 AM (#4)

I always default variables to null.

There are a few reasons for this...

Empty String ("") is not the same as "no value". It has a 0-byte value assigned to it. Null has no value assigned to it.
Empty String will also equate to a value in SQL. So if you insert an empty string into a nullable column, the inserted value will NOT be null.. this is important in differentiating records that were intentionally set to an empty value and records that are just not set.
(boolean) "" equates to false whereas (boolean) null equates to null
(int) "" equates to 0 whereas (int) null equates to null
If you want to allow a value to be set to an empty string, there's no way with "" to check if the value has been changed from its default state. null allows the use of is_null() to differentiate.
null also works for objects and arrays. For example, if i want a method that takes an array as a parameter, but it's optional, I can do function foo(array $bar = null) { }. Then you can test internally vs. null to see if the array has been provided.
Lots of other little organizational benefits... it's always good to have more information than less.

**mlseim** · February 5 '10, 03:47 PM (#5)

LOL ...

medlington,
There you go ... the difference between a "transistor hardware tinkerer" (myself), and a "PHP programming nerd" (Steven).

I think the nerds will end-up ruling the Earth, so you might want to go with Steven

medlington · February 8 '10, 10:07 AM (#6)

Thanks guys,

I would lable myself more of a tinkerer but the nerds normally do things properly so Il try to do things with Nulls in future