根据特定键在对象数组中查找重复项

Question

my goal is to find duplicates in an array of objects, but only for specific object-variables.

Instead of using two foreach-loops like the following, I am searching for a better (more elegant) way to find the duplicates:

foreach ($data as $date) {
      foreach ($data as $innerDate) {
          if ($date->birthday == $innerDate->birthday &&
              $date->street == $innerDate->street &&
              $date->streetnr == $innerDate->streetnr &&
              $date->zipcode == $innerDate->zipcode &&
              $date->twinid == $innerDate->twinid &&
              $date !== $innerDate) {
              // Duple
        }
    }
}

Thanks!

---

Now, I'm using following code, based on Tarilo's idea:

usort($data, function($obj_a, $obj_b){
      if ($obj_a->birthday == $obj_b->birthday &&
          $obj_a->street == $obj_b->street &&
          $obj_a->streetnr == $obj_b->streetnr &&
          $obj_a->zipcode == $obj_b->zipcode &&
          $obj_a->twinid == $obj_b->twinid) {
          // Duple
      }
});

Looks much better than two foreach-Loops ;-)

Answer 1

You could sort the array first and then loop over the sorted array. This way you only have to compare the current object with the next/previous object. Your current algorithm is O(n^2) efficient but after sorting it would be (sorting + looping) = (O(log n) + O(n)) efficient. Where n is the number of objects in your array.