empty(3) [php man page]

EMPTY(3)								 1								  EMPTY(3)

empty - Determine whether a variable is empty

SYNOPSIS

       bool empty (mixed  $var)

DESCRIPTION

	Determine  whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals FALSE.
       empty(3) does not generate a warning if the variable does not exist.

PARAMETERS

	      o $var
		- Variable to be checked

	      Note

		      Prior to PHP 5.5, empty(3) only supports variables; anything else will result in a parse error. In other words, the  follow-
		     ing will not work: empty(trim($name)). Instead, use trim($name) == false.

	       No  warning  is generated if the variable does not exist. That means empty(3) is essentially the concise equivalent to !isset($var)
	      || $var == false.

RETURN VALUES

	Returns FALSE if $var exists and has a non-empty, non-zero value. Otherwise returns TRUE.

	The following things are considered to be empty:

	      o "" (an empty string)

	      o 0 (0 as an integer)

	      o 0.0 (0 as a float)

	      o "0" (0 as a string)

	      o NULL

	      o FALSE

	      o array() (an empty array)

	      o $var; (a variable declared, but without a value)

CHANGELOG

       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.5.0	|						    |
       |	|						    |
       |	| empty(3) now supports  expressions,  rather  than |
       |	| only variables.				    |
       |	|						    |
       | 5.4.0	|						    |
       |	|						    |
       |	|  Checking  non-numeric offsets of strings returns |
       |	| TRUE. 					    |
       |	|						    |
       +--------+---------------------------------------------------+
EXAMPLES

       Example #1

	       A simple empty(3) / isset(3) comparison.

	      <?php
	      $var = 0;

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

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

       Example #2

	      empty(3) on String Offsets

	       PHP 5.4 changes how empty(3) behaves when passed string offsets.

	      <?php
	      $expected_array_got_string = 'somestring';
	      var_dump(empty($expected_array_got_string['some_key']));
	      var_dump(empty($expected_array_got_string[0]));
	      var_dump(empty($expected_array_got_string['0']));
	      var_dump(empty($expected_array_got_string[0.5]));
	      var_dump(empty($expected_array_got_string['0.5']));
	      var_dump(empty($expected_array_got_string['0 Mostel']));
	      ?>

	      Output of the above example in PHP 5.3:

	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)

	      Output of the above example in PHP 5.4:

	      bool(true)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(true)
	      bool(true)

NOTES

       Note

	      Because this is a language construct and not a function, it cannot be called using variable functions.

       Note

	       When using empty(3) on inaccessible object properties, the __isset() overloading method will be called, if declared.

SEE ALSO

       isset(3), __isset(), unset(3), array_key_exists(3), count(3), strlen(3), The type comparison tables.

PHP Documentation Group 														  EMPTY(3)

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SPLOBJECTSTORAGE(3)							 1						       SPLOBJECTSTORAGE(3)

The SplObjectStorage class

INTRODUCTION

	The  SplObjectStorage  class  provides	a map from objects to data or, by ignoring data, an object set. This dual purpose can be useful in
       many cases involving the need to uniquely identify objects.

CLASS SYNOPSIS

       SplObjectStorage

       SplObjectStorageCountableIteratorSerializableArrayAccess

       Methods

       o public void SplObjectStorage::addAll (SplObjectStorage  $storage)

       o public void SplObjectStorage::attach NULL (object  $object, [mixed  $data])

       o public bool SplObjectStorage::contains (object  $object)

       o public int SplObjectStorage::count (void  )

       o public object SplObjectStorage::current (void	)

       o public void SplObjectStorage::detach (object  $object)

       o public string SplObjectStorage::getHash (object  $object)

       o public mixed SplObjectStorage::getInfo (void  )

       o public int SplObjectStorage::key (void  )

       o public void SplObjectStorage::next (void  )

       o public bool SplObjectStorage::offsetExists (object  $object)

       o public mixed SplObjectStorage::offsetGet (object  $object)

       o public void SplObjectStorage::offsetSet NULL (object  $object, [mixed	$data])

       o public void SplObjectStorage::offsetUnset (object  $object)

       o public void SplObjectStorage::removeAll (SplObjectStorage  $storage)

       o public void SplObjectStorage::removeAllExcept (SplObjectStorage  $storage)

       o public void SplObjectStorage::rewind (void  )

       o public string SplObjectStorage::serialize (void  )

       o public void SplObjectStorage::setInfo (mixed  $data)

       o public void SplObjectStorage::unserialize (string  $serialized)

       o public bool SplObjectStorage::valid (void  )

EXAMPLES

       Example #1

	      SplObjectStorage as a set

	      <?php
	      // As an object set
	      $s = new SplObjectStorage();

	      $o1 = new StdClass;
	      $o2 = new StdClass;
	      $o3 = new StdClass;

	      $s->attach($o1);
	      $s->attach($o2);

	      var_dump($s->contains($o1));
	      var_dump($s->contains($o2));
	      var_dump($s->contains($o3));

	      $s->detach($o2);

	      var_dump($s->contains($o1));
	      var_dump($s->contains($o2));
	      var_dump($s->contains($o3));
	      ?>

	      The above example will output:

	      bool(true)
	      bool(true)
	      bool(false)
	      bool(true)
	      bool(false)
	      bool(false)

       Example #2

	      SplObjectStorage as a map

	      <?php
	      // As a map from objects to data
	      $s = new SplObjectStorage();

	      $o1 = new StdClass;
	      $o2 = new StdClass;
	      $o3 = new StdClass;

	      $s[$o1] = "data for object 1";
	      $s[$o2] = array(1,2,3);

	      if (isset($s[$o2])) {
		  var_dump($s[$o2]);
	      }
	      ?>

	      The above example will output:

	      array(3) {
		[0]=>
		int(1)
		[1]=>
		int(2)
		[2]=>
		int(3)
	      }

PHP Documentation Group 												       SPLOBJECTSTORAGE(3)

Linux and UNIX Man Pages

empty(3) [php man page]

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