How to turn get the value of json format to array

I get this value from dd($data); I write this code in laravel. I want to get the value to put in an array so that i can implode the array into string. I cannot implode it in this format.

Collection {#521 ▼
#items: array:1 [▼
0 => {#515 ▼
  +"pdrm_dd": 15
  +"pdrm_mm": "0"
  +"pdrm_yy": 2007
  }
 ]
}

How to turn this result to:

 0 => {15, 0, 2007}

Thank you

via Chebli Mohamed