數組比對並求得對應關係,該怎麼解決

數組比對並求得對應關係
已知數組a：

$a = array (
  0 => 
  array (
    'packageno' => 'S2Y140805025',
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4212',
  ),
  1 => 
  array (
    'packageno' => 'S2Y140805025',
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4214',
  ),
  2 => 
  array (
    'packageno' => 'SYS140804073',
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4212',
  ),
  3 => 
  array (
    'packageno' => 'SYS140804073',
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4213',
  ),
  4 => 
  array (
    'packageno' => 'SYS140731064',
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4154',
  ),
  5 => 
  array (
    'packageno' => 'SYS140731064',
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4210',
  ),
  6 => 
  array (
    'packageno' => 'SYS140801090',
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4200',
  ),
  7 => 
  array (
    'packageno' => 'SYS140801090',
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4210',
  ),
);

有對應關係，例如 packageno S2Y140805025 對應 lotno 4212，4214（type為ECS0-235，cust_no為12654172時）

又知數組b：

$b = array (
  0 => 
  array (
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4211',
  ),
  1 => 
  array (
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4212',
  ),
  2 => 
  array (
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4213',
  ),
  3 => 
  array (
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4214',
  ),
  4 => 
  array (
    'type' => 'ECS0-235',
    'cust_no' => '12654172',
    'lotno' => '4216',
  ),
  5 => 
  array (
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4154',
  ),
  6 => 
  array (
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4200',
  ),
  7 => 
  array (
    'type' => 'ECS1-713',
    'cust_no' => '12657727',
    'lotno' => '4210',
  ),
);

問：當數組a和b的type和cust_no相同時，數組a中的packageno對應的lotno在數組b中是否連續，如果不連續，則將packageno顯示出來。

請問如何處理？
------解決方案--------------------

function foo($a, $b) {
  foreach($a as $v) {
    $c[] = array_search($v, $b);
  }
  for($i=1; $i    if(abs($c[$i] - $c[$i-1]) != 1) {
      return '不連續';
    }
  }
  return '連續';
