How to remove duplicate element in multidimensional passive?

Question

PHP

For example, there is such an array:

$array[$i][0] - date
$array[$i][1] - id
It is necessary to make sure that there is only one id for one date, without repetitions
ps time should not be taken into account
How What's the best way to go on such an adventure? There were ideas with cycles, but I don’t know if this is advisable, suddenly there are some better solutions, thank you in advance (: