array_unique对于简单数组不一致[重复]

Why is it that

echo json_encode(array_unique([1,2,3,4,4]));

Outputs

[1,2,3,4]

And

echo json_encode(array_unique([1,2,3,3,4]));

Outputs

{"0":1,"1":2,"2":3,"4":4}

This has lead to some very odd bugs for me, and I simply cannot understand what's going on here. I just want to remove the duplicates from the array and have it returned as an array.

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array_unique([1,2,3,4,4]) returns:

array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [3]=>
  int(4)
}

Note that the keys are sequential

While array_unique([1,2,3,3,4])) returns:

array(4) {
  [0]=>
  int(1)
  [1]=>
  int(2)
  [2]=>
  int(3)
  [4]=>
  int(4)
}

Note the jump between the key 2 and the key 4.

Because of that - json_encode will omit the keys in the first array (and keep it as array object), while in the second array - the json_encode will look at your array as object and will keep the keys.

You can use array_values (to get the values and ignore the keys).