I want to make Sudoku 16x16 or 25x25 with less computation.

public function make()
{
  // the number of blocks in Sudoku
  $blkNum = 9;

  // US>Initialize Mass
  for($i=0;$i<$blkNum;$i++){
    for($j=0;$j<$blkNum;$j++){
      $d[$i][$j]=-1;
    }
  }

  // Set start to upper left
  $sx = 0;
  $sy = 0;
  $d[$sx][$sy] = land(1,$blkNum); // set start to init

  // move vector
  $dx = [0,1,0, -1,0];
  $dy = [0,0,1,0,-1];

  $queue = [[$sx,$sy]];
  // 0 : x
  // [1]—y

  while($queue){
    $now=array_shift($queue);
    for($i=0;$i<5;$i++) {//vector movement num
      // nx,ny —After move mass
      $nx = $now[0]+$dx[$i];
      $ny = $now[1]+$dy[$i];

      if($nx>=0&$nx<$blkNum&$ny>=0&$ny<$blkNum&&isset($d[$nx][$ny])&$d[$nx][$ny]==-1){
        // calculate the value to be inserted into
        // *If you are doing something, pass the value at random, and if you do not duplicate it in rows, columns, or blocks, you will adopt the value.
        $calc=$this->__put($d,$nx,$ny,range(1,$blkNum)));
        if($calc['result']===true){// If successful, enter a value and push it
          $d[$nx][$ny] = $calc['value'];
          array_push($queue,[$nx,$ny]);
        } else {// When the value is not successful
          // Initialize overlapping parts.
          // push through the queue
          $d[$nx][$ny]=-1;
          $d[$calc['err_x']][$calc['err_y']]=-1;
          array_push($queue, [$calc['err_x', $calc['err_y']]]);
          array_push($queue,[$nx,$ny]);
        }
      }
    }
  }
}

/**
* get a value for the __put parameter
*
*/
private function__put($d,$nx,$ny,$param) 
{
  // take a random array with a queue
  shuffle($param);
  while($param){
    $p = array_shift($param);
    // Check values (overlapping checks in rows, columns, and blocks)
    $check = $this->__check($d, $nx, $ny, $p);
    if($check['result']===true) {//check ok->return
      return ['result'=>true,'value'=>$p];
    } Reduce else {// check NG->param and regression
      if($param){
        return$this->__put($d,$nx,$ny,$param);
      } Else {//param not present
        // Return x,y caught in duplicate check because there was no value until the end.
        return ['result'=>false,'value'=>$p,'err_x'=>$check['x'],'err_y'=>$check['y']);
      }
    }
  }
}