PHP的变量变量和数组或直接代码？

/*DYNAMIC CODING */

$fields = array(
  \'field1\', \'field2\',
  \'field3\', \'field4\',
  \'field5\', \'field6\',
  \'fiel\'... ...);

foreach($fields as $f)
  $$f = $this->input->post($f);

/* OR LITERAL CODING? */

  $field1 = $this->input->post(\'field1\');
  $field2 = $this->input->post(\'field2\');
  $field3 = $this->input->post(\'field3\');
  $field4 = $this->input->post(\'field4\');
  $field5 = $this->input->post(\'field5\');
  $field6 = $this->input->post(\'field6\');
  $field7 = $this->...