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PHP: Comparing Objects using == and ===

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Here are a few examples that show how the relationship between objects and references

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  1. <?php
  2.  
  3. class Box{
  4. 	public $name = "box";
  5. }
  6.  
  7. $box = new Box();
  8. $box_reference = $box;
  9. $box_clone = clone $box;
  10.  
  11. $box_changed = clone $box;
  12. $box_changed->name = "changed box";
  13.  
  14. $another_box = new Box();
  15.  
  16. // Attributes are pretty much the same
  17. echo $box == $box_reference ? 'true' : 'false'; 
  18. echo "<br />";
  19. echo $box == $box_clone ? 'true' : 'false'; 
  20. echo "<br />";
  21. echo $box == $box_changed ? 'true' : 'false'; 
  22. echo "<br />";
  23. echo $box == $another_box ? 'true' : 'false'; 
  24. echo "<br />";
  25. echo "<br />";
  26. // Checks to see if they reference the same object
  27. echo $box === $box_reference ? 'true' : 'false'; 
  28. echo "<br />";
  29. echo $box === $box_clone ? 'true' : 'false'; 
  30. echo "<br />";
  31. echo $box === $box_changed ? 'true' : 'false'; 
  32. echo "<br />";
  33. echo $box === $another_box ? 'true' : 'false'; 
  34. echo "<br />";
  35.  
  36. ?>

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