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PHP : Function Reference : Variable Handling Functions : empty


Determine whether a variable is empty (PHP 4, PHP 5)
bool empty ( mixed var )

Example 2582.  A simple empty() / isset() comparison.

= 0;

// Evaluates to true because $var is empty
if (empty($var)) {
'$var is either 0, empty, or not set at all';

// Evaluates as true because $var is set
if (isset($var)) {
'$var is set even though it is empty';

Related Examples ( Source code ) » empty

Code Examples / Notes » empty


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


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;

karl jung

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);

antone roundy

There's a faster and easier to write method than (isset($a) && strlen($a)) -- isset($a{0}). It evaluates to false if $a is not set or if it has zero length (ie. it's first character is not set). My tests indicate that it's about 33% faster.


The two following methods will do exactly the same, in any case:
// 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).


the php cheatsheet gives a good overview for empty(), isSet(), is_null() etc.
to chris at chaska dot com:
that line
if ( ! isset( $var ) ) return TRUE;
won't do anything, it's useless in that scope.


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.
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 - ";
echo "2. empty string - yes - ";
$var = "";
echo "3. zero string - no - ";
$var = "0";
echo "4. zero number - no - ";
$var = 0;
echo "5. null string - yes - ";
$var = null;
echo "6. single space - yes - ";
$var = " ";
echo "7. several space - yes - ";
$var = "    ";
echo "8. true - no - ";
$var = true;
echo "9. false - no - ";
$var = false;
echo "10. empty array - yes - ";
$var = array();
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


The empty function will not work on an attribute of an object when the object uses the __get method.
The following code:
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

15-mar-2007 10:02

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).


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.
 $spaces = "       ";
 /* This will return false! */
 if (empty($spaces))
    print "This will never be true!";
    print "Told you!";
To make empty() behave the way you would expect it to, use str_replace().
 $spaces = str_replace(" ","","      ");
 /* This will return true! */
 if (empty($spaces))
     print "This will always be true!";
     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.


Since I didn't like how empty() considers 0 and "0" to be empty (which can easily lead to bugs in your code), and since it doesn't deal with whitespace, i created the following function:
function check_not_empty($s, $include_whitespace = false)
   if ($include_whitespace) {
       // make it so strings containing white space are treated as empty too
       $s = trim($s);
   return (isset($s) && strlen($s)); // var is set and not an empty string ''
Instead of saying if (!empty($var)) { // it's not empty } you can just say if (check_not_empty($var)) { // it's not empty }.
If you want strings that only contain whitespace (such as tabs or spaces) to be treated as empty then do: check_not_empty($var, 1)
If you want to check if a string IS empty then do: !check_not_empty($var).
So, whenever you want to check if a form field both exists and contains a value just do: if (check_not_empty($_POST['foo'], 1))
no need to do if (isset() && !empty()) anymore =]


Since a few people here mentioned that empty will not work with magic-overloading ("__get($var)"):
empty(..) goes the same way as isset(..) do, to check if a property exists. Thus you have to override the magic-function __isset($var) to produce correct results for empty(..) in combination with a magic-overloaded property.


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.


Re: inerte is my 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().
   $str = '0';
   // outputs 'empty'
   echo empty($str) ? 'empty' : 'not empty';
   // outputs 'not empty'
   echo $str == '' ? 'empty' : 'not empty';


RE: Arian's comments on
empty( $someClass->someMethod() )
causing Fatal error: Can't use method return value in write context in ...
As retardedly simple as it is, just do this:
function emptyReturn( $var )
 return empty( $var );
and substitute emptyReturn() anywhere you would use empty() on a function call.
I'm telling myself there's some good reason it is this way, but I'm not believing me.


Note the exceptions when it comes to decimal numbers:
$a = 0.00;
$b = '0.00';
echo (empty($a)? "empty": "not empty"); //result empty
echo (empty($b)? "empty": "not empty"); //result not empty
$c = intval($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.
TABLE t has columns id MEDIUMINT and d DECIMAL(4,2)
and contains 1 row where id=1, d=0.00
$q = "SELECT * FROM t";
$res = mysql_query($q);
$row = mysql_fetch_assoc($res);
echo (empty($row['d'])? "empty": "not empty"); //result not empty

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.)
if (!empty($_POST['name'])) $name = $_POST['name'];
compared to isSet(), this saves an extra step. using !empty() will check if the variable is not empty, and if the variable doesnt exit, no warning is generated.
with isSet(), to acheive the same result as the snippit above, you would need to do this:
if (isSet($_POST['name']) && $_POST['name']) $name = $_POST['name'];
so using !empty() reduces code clutter and improves readability, which IMO, makes this VERY usefull.


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.";
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!


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.

chris baynes

In response to a previous post regarding the speed of:
if (empty($var))
if (!$var)
if (!empty($var))
if ($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.


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".


If you are writing a form handling script and just need to check whether a required field has been filled in, you can just use strlen() to check the field.  It handles all the cases properly when you are only dealing with strings.
$x = "0";
echo strlen($x);  // returns 1
$x = "";
echo strlen($x);  // returns 0
unset $x
echo strlen($x);  // returns 0
In other words, the check you need to make becomes:
if (strlen($email) == 0)
  $error = "Please enter your email address";
if (strlen($_POST["email"]) == 0)
  $error = "Please enter your email address";
Hopes this helps anyone just seeking a workaround for the annoying empty("0") anomaly.


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 (!$blah)
if (empty($blah))
if ($blah)
if (!empty($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.


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...)
function is_extant($var)
if (isset($var))
if ( empty($var) && ($var !== 0) && ($var !== '0') )
return FALSE;
return TRUE;
return FALSE;


Here's what I do for the zero issue issue:
if($val == '' && $val !== 0 && $val !== '0')

talus talusch dot no dot spam

I made something better than fnbh at freemail dot hu in order to put more variables as an arg into the empty function (like isset, you can put every var you want to, if one is not set, then it returns false : the behaviour of this function will do the same, except that if one of the variables if empty, then it returns true). But, I made it the simpliest way, and also i'm usign the foreach structure, which is, i believe so, is better than the for structure for an array.
Here it comes :
function multi_empty(){
// -- If no parameters, then it is empty (just a matter of logic, nah ?).
if( func_num_args() == 0 ){
return true;

$args = func_get_args();

// -- Getting through all the arguments. If there's one which is empty, then we return true : there is no reason to continue... ;)
foreach($args as $arg){
if( empty($arg) ){
return true;

// -- Nothing was found empty ; then the result is false.
return false;


for beginers:
function empty_vars() {
// if ((empty($var1)) || (empty($var2)) .... ) (lazy func)
if (func_num_args()==0) return true;
   for ($i = 0; $i < $vars; $i++) {
       if (empty($vars[$i])) {
return true;
return false;


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.

inerte is my username

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.


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!!!


But not faster than
if (!$var)
which is about 20% faster than empty() on php5.1


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:
 $spaces = "        ";
    echo "Omg empty string.";
     echo "Omg the string isnt empty!";
 Hope that helps anyone, though it is rather trivial.
i think is said above that empty(trim($spaces)) dont work
,i think is better to seperate this two function
 empty($spaces) thern continue with the code......

myfirstname dot barros

$a = Array( ); #<- empty
$a = Array( '' ); #<- NOT empty
$a = Array( Null ); #<- NOT empty

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