isset vs empty vs is_null

Question

I\'m trying to write a script that when a user uploads a file and does not enter a name an error is returned. I\'ve tried using is_null, empty, and isset and they all do not

Answer 1

Ref this: different between isset, is_null, empty in PHP

• isset() mean $var is defined and not null
• is_null() mean $var is defined and null. throw an error if it is undefined.
• empty() is anything mean NO => false, 0, 0.0, "", "0", null, array()

Answer 2

isset()

From PHP manual – isset():

isset — Determine if a variable is set and is not NULL

In other words, it returns true only when the variable is not null.

empty()

From PHP Manual – empty():

empty — Determine whether a variable is empty

In other words, it will return true if the variable is an empty string, false, array(), NULL, “0?, 0, and an unset variable.

is_null()

From PHP Manual – is_null():

is_null — Finds whether a variable is NULL

In other words, it returns true only when the variable is null. is_null() is opposite of isset(), except for one difference that isset() can be applied to unknown variables, but is_null() only to declared variables.

Answer 3

Here is a very good explanation:

Answer 4

is_null is the dual of isset except isset does not print notices if the variable is null.

>$ciao;
>var_export(is_null($ciao));
>PHP Notice:  Undefined variable: ciao in php shell code on line 1
>true
>var_export(!isset($ciao));
>true

Answer 5

1. isset() — Determine if a variable is set and not NULL

2. empty() - Determine if a variable is empty.

3. is_null() - Determine if a variable is null

Answer 6

You can try this :

if(!isset($_REQUEST['name_input_name']))
{
    $file->error = 'Please Enter a Title';
    return false;
}
$caption = $_REQUEST['name_input_name'];

Note : $_REQUEST is an Global array that store the data in key=>value pair. consider "name_input_name" as value extracted from server.

if name_input_name is set to some value code will skip if block and store the value to variable $caption.