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Last updated: Thu, 03 May 2007

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empty

(PHP 4, PHP 5)

empty — 変数が空であるかどうかを検査する

説明

bool empty ( mixed $var )

変数が空であるかどうかを検査する

パラメータ

var

チェックする変数

注意: empty() は、変数のみをチェックし、それ以外の値を チェックすると文法エラーを生成します。つまり、次の例は動作しません: empty(trim($name)).

empty()は、変数が設定されていないときに警告が生成 されないことを除けば、(boolean) var の逆です。

返り値

varが空でないか、0でない値であれば FALSE を返します。

次のような値は空であると考えられます。:
"" (空文字列)
0 (0 は整数)
"0" (0は文字列)
NULL
FALSE
array() (空の配列)
var $var;(変数が宣言されているが、クラスの中で値が設定されていない)

変更履歴

バージョン説明
PHP 5

PHP5では、プロパティがないオブジェクトは空でないと見なされます。

PHP 4

PHP 4では、文字列 "0"は空であると見なされます。

例

例 2478. 簡単な empty() / isset() の比較

<?php
$var = 0;

// $var が空なのでtrueと評価されます
if (empty($var)) {
    echo '$var is either 0, empty, or not set at all';
}

// $var が設定されているのでtrueと評価されます
if (isset($var)) {
    echo '$var is set even though it is empty';
}
?>

注意

注意: これは、関数ではなく 言語構造のため、可変関数 を用いて コールすることはできません。

参考

isset()
unset()
array_key_exists()
count()
strlen()
PHP 型の比較表



add a note add a note User Contributed Notes
empty
M
24-Mar-2007 10:32
The empty() function is not exactly useful.... it defines both "0" and 0 (the numerical version) as empty. That's not really true is it!

Consider a user updating a record and setting a value to 0. When the form is posted and empty() is used to check for empty values it will return true. If you are testing for a mandatory field this will fail... even though the field has a value.

The following checks if a field is "really" empty, and includes as many test cases as I could think of.

<?php
function isempty($var) {
    if (((is_null($var) || rtrim($var) == "") && $var !== false) || (is_array($var) && empty($var))) {
        echo "yes<br />";
    } else {
        echo "no<br />";
    }
}

echo "1. unset variable - yes - ";
isempty($unset);

echo "2. empty string - yes - ";
$var = "";
isempty($var);

echo "3. zero string - no - ";
$var = "0";
isempty($var);

echo "4. zero number - no - ";
$var = 0;
isempty($var);

echo "5. null string - yes - ";
$var = null;
isempty($var);

echo "6. single space - yes - ";
$var = " ";
isempty($var);

echo "7. several space - yes - ";
$var = "    ";
isempty($var);

echo "8. true - no - ";
$var = true;
isempty($var);

echo "9. false - no - ";
$var = false;
isempty($var);

echo "10. empty array - yes - ";
$var = array();
isempty($var);
?>

The output from this should be...

1. unset variable - yes - yes
2. empty string - yes - yes
3. zero string - no - no
4. zero number - no - no
5. null string - yes - yes
6. single space - yes - yes
7. several space - yes - yes
8. true - no - no
9. false - no - no
10. empty array - yes - yes

Regards,
M
16-Mar-2007 07:02
Speed comparisons between empty($foo) versus !$foo are pointless; you're saving what, a couple dozen nanoseconds? If you care that much you'll have to benchmark every single new version of PHP in case changes affect the relative speeds of your various methods, and then recode if one method overtakes another. Now THAT is a waste of time.

Far more important is that your code says what you want it to mean.

Besides, when $foo is not set empty($foo) is >1400% faster than !$foo (and that's AFTER suppressing the notice message).
Arian
03-Feb-2007 12:35
Read the above note carefully: "Note:  empty() only checks variables as anything else will result in a parse error."

Took me forever to google around and figure out this error was related to above lines:
[02-Feb-2007 09:38:09] PHP Fatal error:
Can't use function return value in write context in blah.php on line ##

So hopefully someone else googling the error text itself, will track back to this page.

It would be nice though if empty() can 'correctly' parse and return a value for a function call within itself like other funcs.
Chris Baynes
02-Feb-2007 05:39
In response to a previous post regarding the speed of:

if (empty($var))
versus
if (!$var)

or

if (!empty($var))
versus
if ($var)

In fact I found that the empty() function is always slower. I have tested this on three different machines; Celeron, Pentium M, and an AMD Athlon 64. These all run php 5.2, and I have repeated the tests a number of times using different loops and variable types. My results show that, on average, empty() takes around 15 - 20% longer to complete its task.
Stephen
22-Jan-2007 07:08
I wanted to correct a couple of errors in some earlier user notes, regarding which is better, using empty() within an if clause to be evaluated, or using only the variable. E.g.:

if (!$blah)

versus

if (empty($blah))

or

if ($blah)

versus

if (!empty($blah))

First, one person noted that empty() is basically worthless because you don't need it to do the above functionality. However, I think this is wrong for 2 reasons:

1. It is needed for arrays and (I think) objects
2. empty() is actually FASTER than using just the variable. You might think that it would be slower because it looks like a function, but it is actually a language construct. Apparently it is optimized. It is at least 10% faster, sometimes nearly 20% faster.

Second, one person claimed that if you don't use empty, and just test the variable, you will get an E_WARNING error. I don't know if this used to be true, but for me in PHP 5.2, it only generates an E_NOTICE.

I hope this clears up somebody's confusion.
fnbh at freemail dot hu
09-Jan-2007 08:13
for beginers:
function empty_vars() {
    // if ((empty($var1)) || (empty($var2)) .... ) (lazy func)
    if (func_num_args()==0) return true;
    $vars=func_get_args();
    for ($i = 0; $i < $vars; $i++) {
        if (empty($vars[$i])) {
            return true;
            }
        }
    return false;
    }
prikkeldraad at gmail dot com
16-Nov-2006 12:14
The empty function will not work on an attribute of an object when the object uses the __get method.

The following code:
<?php
class Person {
    protected $name_;

    public function __construct($name) {
        $this->name_ = $name;
    }

    public function __get($name) {
        // just return name
        return $this->name_;
    }
}

class FirstPerson extends Person {
    public function __construct() {
        parent::__construct('The great cornholio');
    }

    public function __get($name) {
        return parent::__get($name);
    }
}

$tgc = new FirstPerson;

print 'Name: '.$tgc->name.'<br />';

if (!empty($tgc->name)) {
    print 'Name via getter is not empty';
} else {
    print 'Name via getter is empty';
}
?>

Results in:
Name: The great cornholio
Name via getter is empty
r-u-d-i-e at jouwmoeder dot dot nl
10-Jul-2006 11:45
The two following methods will do exactly the same, in any case:
<?php

// CASE 1
if ( empty($var) )
{
    // do your thing
}

// CASE 2
if ( !isset($var) || !$var )
{
    // do that same thing
}

?>
empty( ) checks for isset AND also the value of the variable (0, "0", "", etc).
Karl Jung
04-Jun-2006 01:03
This function I did, works like empty(), but doesn't consider zero (0) as empty.
Also, considers as empty, a string containing only blank spaces, or "\n", "\t", etc.

function my_empty($val)
{
    $result = false;
   
    if (empty($val))
        $result = true;

    if (!$result && (trim($val) == ""))
        $result = true;

    if ($result && is_numeric($val) && $val == 0)
        $result = false;

    return $result;
}

Values considered as EMPTY:

$val = "";
$val = "  ";
$val = " \t \n ";
$val = array();
$val = false;
$val = null;

Values considered NOT EMPTY:

$val = "0";
$val = intval(0);
$val = floatval(0);
boards at gmail dot com
29-Apr-2006 03:53
Followup to ben at wbtproductions dot com:

You'll want to do this check for numeric 0:
<?
if ($data === 0) echo 'The data is zero.';
?>

Checking $data == 0 basically means the same thing as "is $data false?".  Loose type checking is a gotcha you should look out for.
ben at wbtproductions dot com
19-Apr-2006 09:40
It is important to note that empty() does not check data type.  This can change the functioning of any program if, at some point, your data might be all zeroes, containing no real data, but also not empty by PHP's definition.

Think about this:
$data = "00000";
if (empty($data))
echo "The data appears empty.";

if (0==$data) //Use this test for number applications!!
echo "The data is zero.";

$data = 0;
if (empty($data))
echo "Remember, zero is empty.";

outputs:
The data is zero.
Remember, zero is empty.

This could crop up in ZIP codes and phone numbers or zero-filled/zero-padded values from SQL.  Watch those variable types!
nobody at example dot com
01-Mar-2006 05:06
Re: inerte is my gmail.com username's comment:

While that may be true, those two statements (empty($var), $var == '') are NOT the same. When programming for web interfaces, where a user may be submitting '0' as a valid field value, you should not be using empty().

<?php
    $str = '0';

    // outputs 'empty'
    echo empty($str) ? 'empty' : 'not empty';

    // outputs 'not empty'
    echo $str == '' ? 'empty' : 'not empty';
?>
Trigunflame at charter dot net
01-Feb-2006 02:35
But not faster than

if (!$var)
{

}

which is about 20% faster than empty() on php5.1
inerte is my gmail.com username
11-Nov-2005 11:58
empty() is about 10% faster than a comparision.

if (empty($var)) {
}

is faster than:

if ($var == '') {
}

YMMV, empty() also checks array and attributes, plus 0, and '' is kind a string with nothing inside. But I was using '' and got a huge performance boost with empty().

PHP 4.3.10-15, Apache/2.0.54, Kernel 2.4.27-2-386.
nahpeps at gmx dot de
19-Aug-2005 07:14
When using empty() on an object variable that is provided by the __get function, empty() will always return true.

For example:
class foo {
  
   public function __get($var) {
      if ($var == "bar") {
         return "bar";  
      }  
   }  
}
$object_foo = new foo();
echo '$object_foo->bar is ' . $object_foo->bar;
if (empty($object_foo->bar)) {
   echo '$object_foo->bar seems to be empty';  
}

produces the following output:
$object_foo->bar is bar
$object_foo->bar seems to be empty
jmarbas at hotmail dot com
02-Jul-2005 01:10
empty($var) will return TRUE if $var is empty (according to the definition of 'empty' above) AND if $var is not set.

I know that the statement in the "Return Values" section of the manual already says this in reverse:

"Returns FALSE if var has a non-empty and non-zero value."

but I was like "Why is this thing returning TRUE for unset variables???"... oh i see now... Its supposed to return TRUE for unset variables!!!

<?php
  ini_set('error_reporting',E_ALL);
  ini_set('display_errors','1');
  empty($var);
?>
nsetzer at allspammustdie dot physics dot umd dot edu
01-Jul-2005 12:02
I needed to know if the variable was empty, but allow for it to be zero, so I created this function.  I post it here in case anybody else needs to do that (it's not hard to make, but why reinvent the wheel...)

<?php
function is_extant($var)
{
if (isset($var))
    {
    if ( empty($var) && ($var !== 0) && ($var !== '0') )
        return FALSE;
    else
        return TRUE;
    }
else
    return FALSE;
}
?>
tan_niao
10-Jun-2005 12:43
admin at prelogic dot net has wrote the following
  In response to admin at ninthcircuit dot info

  The best way around that is the trim function. For example:

  $spaces = "        ";
  if(empty(trim($spaces)){
     echo "Omg empty string.";
  }else{
      echo "Omg the string isnt empty!";
  }

  Hope that helps anyone, though it is rather trivial.

i think is said above that empty(trim($spaces)) dont work
,i think is better to seperate this two function

  trim($spaces);
  empty($spaces) thern continue with the code......
Kouenny
08-Jun-2005 10:45
In response to "admin at ninthcircuit dot info" :

Instead of using "$spaces = str_replace(" ","","      ");"
you should use the function "trim()", which clear spaces before and after the string. e.g. "trim('    example 1           ')" returns "example 1".
shorty114
28-May-2005 08:17
In Response to Zigbigidorlu:

Using if (!$_POST['foo']) is not the best way to test if a variable is empty/set. Doing that creates a E_WARNING error for an uninitialized variable, and if you are planning to use a rather high error level, this is not the better way, since this will create an error whereas if (!isset($_POST['foo'])) or (empty($_POST['foo'])) doesn't echo an error, just returns true/false appropriately.

One example of this is in the phpBB code - the coding guidelines state that you have to use isset() or empty() to see if a variable is set, since they planned to use a higher level of error reporting.
Zigbigidorlu
25-May-2005 02:44
This function is of very little use, as the "!" operator creates the same effect.

<?
 if(empty($_POST['username']) exit;
?>

 has the exact same functionality as:

<?
 if(!$_POST['username']) exit;
?>
admin at ninthcircuit dot info
25-May-2005 02:14
Something to note when using empty():

empty() does not see a string variable with nothing but spaces in it as "empty" per se.

Why is this relevant in a PHP application? The answer is.. if you intend to use empty() as a means of input validation, then a little extra work is necessary to make sure that empty() evaluates input with a more favorable outcome.

Example:
<?php
  $spaces = "       ";
  /* This will return false! */
  if (empty($spaces))
     print "This will never be true!";
  else
     print "Told you!";
?>

To make empty() behave the way you would expect it to, use str_replace().

<?php
  $spaces = str_replace(" ","","      ");
  /* This will return true! */
  if (empty($spaces))
      print "This will always be true!";
  else
      print "Told you!";
?>

This might seem trivial given the examples shown above; however, if one were to be storing this information in a mySQL database (or your preferred DB of choice), it might prove to be problematic for retrieval of it later on.
admin at ninthcircuit dot info
25-May-2005 02:13
Something to note when using empty():

empty() does not see a string variable with nothing but spaces in it as "empty" per se.

Why is this relevant in a PHP application? The answer is.. if you intend to use empty() as a means of input validation, then a little extra work is necessary to make sure that empty() evaluates input with a more favorable outcome.

Example:
<?php
  $spaces = "       ";
  /* This will return false! */
  if (empty($spaces))
     print "This will never be true!";
  else
     print "Told you!";
?>

To make empty() behave the way you would expect it to, use str_replace().

<?php
  $spaces = str_replace(" ","","      ");
  /* This will return true! */
  if (empty($spaces))
      print "This will always be true!";
  else
      print "Told you!";
?>

This might seem trivial given the examples shown above; however, if one were to be storing this information in a mySQL database (or your preferred DB of choice), it might prove to be problematic for retrieval of it later on.
myfirstname dot barros at gmail dot com
30-Apr-2005 12:15
<?php
$a = Array( ); #<- empty
$a = Array( '' ); #<- NOT empty
$a = Array( Null ); #<- NOT empty
?>

---
gabriel
rehfeld.us
23-Aug-2004 05:47
ive found the empty() contruct extremely usefull. For some reason people seem to think its of little use, but thats not so.

for example, form fields can be checked in 1 step by using empty(). (assuming a basic check of whether it was submitted and if submitted, that it was not empty.)

<?php

if (!empty($_POST['name'])) $name = $_POST['name'];

?>

compared to isSet(), this saves an extra step. using !empty() will check if the variable is not empty, and if the variable doesnt exit, no warning is generated.

with isSet(), to acheive the same result as the snippit above, you would need to do this:

<?php

if (isSet($_POST['name']) && $_POST['name']) $name = $_POST['name'];

?>

so using !empty() reduces code clutter and improves readability, which IMO, makes this VERY usefull.
paul at worldwithoutwalls dot co dot uk
23-May-2004 02:09
Note the exceptions when it comes to decimal numbers:

<?php
$a = 0.00;
$b = '0.00';
echo (empty($a)? "empty": "not empty"); //result empty
echo (empty($b)? "empty": "not empty"); //result not empty
//BUT...
$c = intval($b);
echo (empty($c)? "empty": "not empty"); //result empty
?>

For those of you using MySQL, if you have a table with a column of decimal type, when you do a SELECT, your data will be returned as a string, so you'll need to do apply intval() before testing for empty.

e.g.
TABLE t has columns id MEDIUMINT and d DECIMAL(4,2)
and contains 1 row where id=1, d=0.00
<?php
$q = "SELECT * FROM t";
$res = mysql_query($q);
$row = mysql_fetch_assoc($res);
echo (empty($row['d'])? "empty": "not empty"); //result not empty
?>
phpcheatsheet at blueshoes dot org
27-Nov-2002 04:18
the php cheatsheet gives a good overview for empty(), isSet(), is_null() etc. http://www.blueshoes.org/en/developer/php_cheat_sheet/

to chris at chaska dot com:
that line
if ( ! isset( $var ) ) return TRUE;
won't do anything, it's useless in that scope.
add a note add a note

floatval" width="11" height="7"/> <doubleval
Last updated: Thu, 03 May 2007
 
 
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