如何在PHP中检查变量是否为null

Question

In PHP,

I am using One Variable called $token.

I want to check whether it's value is null or not.I have tried by checking empty/isset/is_null in if condition.But It didn't work.

when I print its value using error_log($token) then it gives output like : " (null) ".

Because in database its value is " (null) ".

How can I check in php whether it is (null) or not.

Please guide me on this.

Answer 1

It looks like you're working not with a real null , but with a string - that's literally '(null)' . So check for that instead, with...

if ($token === '(null)') { ... }

What's more important, however, is why this value appeared in the DB in first place. Unless there's a very specific (and valid) reason to do this, you'd better store nulls (absence of information) as plain NULL value, to avoid confusion such in this case both on application and database layer.

Answer 2

What you did is also right. Even You can have some more options try following conditions

1. if($token === null){....}
2. if($token == null){....}
3. if($token == ""){....}

1. init some a string variable

   $tmp_string = ""; $tmp_string .= $token if($tmp_string== ""){....}

Try All above. All The Best....

Answer 3

或最短的方法

if($token) echo 'not null';

Answer 4

我使用strlen() condition解决了我的问题。谢谢大家的建议。