<?php
$numbers = array(
  'М903СЕ197',
  'А777МР97',
  'Е555КХ99',
  'К001РА95',
  'Ошибка',
  'О1234ОО799'
  );
$cyril = array(
  'А','В','Е','К','М','Н','О','Р','С','Т','У','Х'
  );
$latin = array(
  'A','B','E','K','M','H','O','P','C','T','Y','X'
  );

foreach ($numbers as $number) {
  echo 'Входной номер: ' . $number . ' ';
  $number = str_replace($cyril, $latin, $number);
  $pattern = '/([ABEKMHOPCTYX])([0-9]{3})([ABEKMHOPCTYX]{2})([17]{0,1}[0-9]{2})/i';
  preg_match($pattern, $number, $result);
  $result = str_replace($latin, $cyril, $result);
  echo 'Выходной массив: ';
  print_r($result);
}