note 61744 modified in language.references.spot by danbrown

One may check reference to any object by simple operator==( object). Example:

<?php
  class A {}

  $oA1 = new A();

  $roA = & $oA1;

  echo "roA and oA1 are " . ( $roA == $oA1 ? "same" : "not same") . "<br>";

  $oA2 = new A();
  $roA = & $roA2;

  echo "roA and oA1 are " . ( $roA == $oA1 ? "same" : "not same") . "<br>";
?>

Output:

roA and oA1 are same
roA and oA1 are not same

Current technique might be useful for caching in objects when inheritance is used and only base part of extended class should be copied (analog of C++: oB = oA):

<?php
class A { 
  /* Any function changing state of A should set $bChanged to true */
  public function isChanged() { return $this->bChanged; }
  private $bChanged;
  //...
}

class B extends A {
// ...
  public function set( &$roObj) {
    if( $roObj instanceof A) {
      if( $this->roAObj == $roObj &&
          $roObj->isChanged()) {
        /* Object was not changed do not need to copy A part of B */
      } else {
        /* Copy A part of B */
        $this->roAObj = &$roObj;
      }
    }
  }

  private $roAObj;
}
?>

--was--
One may check reference to any object by simple operator==( object). Example:

  class A {}

  $oA1 = new A();

  $roA = & $oA1;

  echo "roA and oA1 are " . ( $roA == $oA1 ? "same" : "not same") . "<br>";

  $oA2 = new A();
  $roA = & $roA2;

  echo "roA and oA1 are " . ( $roA == $oA1 ? "same" : "not same") . "<br>";

Output:

roA and oA1 are same
roA and oA1 are not same

Current technique might be useful for caching in objects when inheritance is used and only base part of extended class should be copied (analog of C++: oB = oA):

class A { 
  /* Any function changing state of A should set $bChanged to true */
  public function isChanged() { return $this->bChanged; }
  private $bChanged;
  //...
}

class B extends A {
// ...
  public function set( &$roObj) {
    if( $roObj instanceof A) {
      if( $this->roAObj == $roObj &&
          $roObj->isChanged()) {
        /* Object was not changed do not need to copy A part of B */
      } else {
        /* Copy A part of B */
        $this->roAObj = &$roObj;
      }
    }
  }

  private $roAObj;
}

http://php.net/manual/en/language.references.spot.php