Difference between value = ""; and value = NULL; in PHP?

Question

What is the difference between value = NULL; and value = ""; in PHP ?

Am facing wierd response as if I set value = ""; than I get empty array response from database which is what am supposed to get but if I set value = NULL; than I get empty string response from mysql database instead of empty array response.

I am not sure why this is the case. Any Suggestions !!!

Is this question about PHP, or about SQL databases? If it is about PHP, how does the database remark factor in? — Thorarin
– Thorarin, Commented Jan 12, 2010 at 16:58

Adriaan Stander · Accepted Answer · 2010-01-12 16:56:46Z

1

Have a look at

Working with NULL Values

The NULL value can be surprising until you get used to it. Conceptually, NULL means “a missing unknown value” and it is treated somewhat differently from other values. To test for NULL, you cannot use the arithmetic comparison operators such as =, <, or <>. Use the IS NULL and IS NOT NULL operators instead.

answered Jan 12, 2010 at 16:56

Adriaan Stander

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David Thomas Over a year ago

No, but it is MySQL, which is also tagged in the question, with no specification of which the question applies to. Up-voted to reduce the karma-hit (and because it's a good answer, obviously).

Community · Accepted Answer · 2017-05-23 11:47:46Z

0

empty strings and NULL are treated differently in MySQL. I had a similar question about this issue:

why use NOT NULL default = ''?

You have 2 solutions here:

Set the database field(s) you are checking to NOT NULL default '' or something similar.
rewrite your queries so that check both cases. ex: 'where field = '' OR field IS NULL'

edited May 23, 2017 at 11:47

CommunityBot

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answered Jan 12, 2010 at 16:58

GSto

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Comments

Parrots · Accepted Answer · 2010-01-12 16:57:17Z

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Value = NULL sets the variable to nothing, basically. Whereas Value = "" sets it to a blank string and while a blank string might look like nothing, it technically is a value of sorts. NULL and "" are both different values.

answered Jan 12, 2010 at 16:57

Parrots

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2 Comments

Parrots Over a year ago

They actually are quite different php.net/manual/en/language.types.null.php : $var = ""; is_null($var) is false.

mr-sk Over a year ago

Ok, your right: <?php if ('' == null) echo " '' == null "; if ('' === null) echo " '' === null "; Outputs: '' == null

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