PHP returns NULL from database as empty string "". Why?

Question

This could be connected to my previous question, and maybe a duplicate to this.

Well, why value declared as NULL in MySQL database is returned as "" (empty string), in this case all my functions which returns some value dependently on result of evaluation, dont' work.

$var = NULL; // false
$var = ""; // true

Also I'm dumping result of evaluating:

var_dump(isset($var));

I'm using PDO DB driver, PHP 5.4.7 and MySQL 5.5.27.

Is that like behaviour expected or is this some bug? NULL is saved in field as MySQL NULL, not string 'NULL'.

Probably it's NULL, do you check this with is_null() or something else? — Wrikken
– Wrikken, Commented Dec 5, 2013 at 16:51

John Conde · Accepted Answer · 2013-12-05 16:51:20Z

4

You need to use is_null() to see if the value is null. NULL is equal to nothing. Even another NULL.

(Plus in your example you use an assignment operator (=) and not a comparison operator (== or ===) but I am sure that is just a typo in your question).

answered Dec 5, 2013 at 16:51

John Conde

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2 Comments

Alan Kis Over a year ago

See edit. If I use is_null() my code will always evaluate to false, because NULL is converted to empty string "".

Alan Kis Over a year ago

Thanks for your effort, stupid me, strip_tags() actually stripped NULL to empty string in my sanitize function. That was last thing I should expected.

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