PHP empty() strange behaviour

Question

The following code (#1):

var_dump($myObject->getBook()->getCollection());
$testArray=Array();
var_dump($testArray);
var_dump(empty($testArray));

...will output:

array(0) { } array(0) { } bool(true)

The following code (#2):

var_dump($myObject->getBook()->getCollection());
$testArray=Array();
var_dump($testArray);
var_dump(empty($myObject->getBook()->getCollection()));

...will output:

Nothing. No error, not a single character. No nothing.

class Book{
  protected $bidArray=Array();
  public function getCollection(){
    return $this->bidArray;
  }
}

What is happening there?

Is displaying errors turned on?

Jasper
– Jasper

2012-04-21 14:38:47 +00:00
Commented Apr 21, 2012 at 14:38 — Jasper
– Jasper, Commented Apr 21, 2012 at 14:38
Yes, they are turned on!

Dyin
– Dyin

2012-04-21 14:39:13 +00:00
Commented Apr 21, 2012 at 14:39 — Dyin
– Dyin, Commented Apr 21, 2012 at 14:39

Crozin · Accepted Answer · 2012-04-21 14:39:27Z

7

empty() is not a function, although it looks like a one. It's just a special syntax that works only with variables, e.g. empty($abc). You simply cannot use expressions such as empty(123) or empty($obj->getSth()).

answered Apr 21, 2012 at 14:39

Crozin

44.5k13 gold badges92 silver badges136 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Dyin Over a year ago

Yeah. Just stored the return value of getCollection() in a variable before using empty(). PHP is sick.

Crozin Over a year ago

@Dyin PHP is sick. - I couldn't agree more. ;)

Andreas Wong · Accepted Answer · 2012-04-21 14:40:51Z

3

You cannot use empty() with anything other than variable (that means no function call as well).

var_dump(empty($myObject->getBook()->getCollection()));

You must have your error display turned off, as the following:

<?php

class Bar {
        function foo() {
        }
}

$B = new Bar();
empty($B->foo());

Gives

PHP Fatal error: Can't use method return value in write context in D:\cw\home\andreas\test\empty.php on line 9

Fatal error: Can't use method return value in write context in D:\cw\home\andreas\test\empty.php on line 9

On my local.

Try doing ini_set('display_errors', true) prior to your var_dump's and see if the error messages crop up

answered Apr 21, 2012 at 14:40

Andreas Wong

60.7k19 gold badges112 silver badges123 bronze badges

2 Comments

Dyin Over a year ago

Tired to set display_errors as you mentioned. Still no output. Got fatal errors from elsewhere BTW. Using PHP 5.3.8 with XAMPP.

Andreas Wong Over a year ago

@Dyin hmm, also try with ini_set('error_reporting', E_ALL) along with display_errors, see if that helps

dan-lee · Accepted Answer · 2012-04-21 14:40:07Z

2

As on php.net

empty() only checks variables as anything else will result in a parse error. In other words, the following will not work: empty(trim($name)).

This is because empty() isn't a function, but a language construct and therefore limited to this behaviour.

answered Apr 21, 2012 at 14:40

dan-lee

14.5k6 gold badges55 silver badges81 bronze badges

Comments

Community · Accepted Answer · 2017-05-23 11:55:53Z

2

Using empty() you can't check directly against the return value of a method. More info here: Can't use method return value in write context

edited May 23, 2017 at 11:55

CommunityBot

11 silver badge

answered Apr 21, 2012 at 14:40

sthzg

5,5642 gold badges32 silver badges51 bronze badges

Collectives™ on Stack Overflow

PHP empty() strange behaviour

4 Answers 4

2 Comments

2 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related