Get an array property inside an object?

Question

PHP

$prefix1='88Qn|Q*wcIa5';
$prefix2='66{Rvi#wy?r?#1';
$arr=[
  'prefix1'=>'88Qn|Q*wcIa5',
  'prefix2'=>'66{Rvi#wy?r?#1',
  'encode'=>"$prefix1$prc$prefix2"
];

How can I replace "$prefix1$prc$prefix2" with something like this to take values ​​from an array and not variables?
this['prefix1'].$prc.this['prefix2']

Answer 1

$prc = '';
  $arr=[
    'prefix1' => '88Qn|Q*wcIa5',
    'prefix2' => '66{Rvi#wy?r?#1',
  ];

  $arr['encode'] = $arr['prefix1'] . $prc . $arr['prefix2'];