计算从“从”到“从”有多少年重力格式中的日期格式

我这里有一个表单(https://nursinggroup.com/pharmacist-profile/)，用户将在"从"输入框和"到"输入框中以"mm/yy"的形式输入日期。在用户浏览并添加所有日期之后，他们提交表单，然后使用Gravity Forms PDF Extended (mPDF)创建PDF。我需要做的是，在创建PDF的过程中，我需要它计算每个项目的值，并将每个项目的总年数输出到PDF中。

例如，如果我在在线表单中输入以下条目:

Ambulatory Care    "From: 02 / 88"   "To: 02 / 98"
Home Healthcare    "From: 07 / 02"   "To: 07 / 05"
Oncology           "From: 09 / 06"   "To: 05 / 12"

在PDF上，它会吐出以下内容:

Ambulatory Care    10
Home Healthcare    3
Oncology           5.8

我已经通读并尝试了许多不同的代码示例，但我只是没有足够的技能与这种类型的PHP使这个工作。还有几件事要记住。这是在一个WordPress网站上，使用Gravity Forms作为表单，并使用Gravity Forms PDF Extended从这些表单创建PDF。另外需要注意的是，年份的输入必须保持yy而不是yyyy的格式。用户也不填写日期，只填写mm / yy

<?php
  // Set timezone
  date_default_timezone_set("UTC");
  // Time format is UNIX timestamp or
  // PHP strtotime compatible strings
  function dateDiff($time1, $time2, $precision = 6) {
    // If not numeric then convert texts to unix timestamps
    if (!is_int($time1)) {
      $time1 = strtotime($time1);
    }
    if (!is_int($time2)) {
      $time2 = strtotime($time2);
    }
    // If time1 is bigger than time2
    // Then swap time1 and time2
    if ($time1 > $time2) {
      $ttime = $time1;
      $time1 = $time2;
      $time2 = $ttime;
    }
    // Set up intervals and diffs arrays
    $intervals = array('year','month','day','hour','minute','second');
    $diffs = array();
    // Loop thru all intervals
    foreach ($intervals as $interval) {
      // Create temp time from time1 and interval
      $ttime = strtotime('+1 ' . $interval, $time1);
      // Set initial values
      $add = 1;
      $looped = 0;
      // Loop until temp time is smaller than time2
      while ($time2 >= $ttime) {
        // Create new temp time from time1 and interval
        $add++;
        $ttime = strtotime("+" . $add . " " . $interval, $time1);
        $looped++;
      }
      $time1 = strtotime("+" . $looped . " " . $interval, $time1);
      $diffs[$interval] = $looped;
    }
    $count = 0;
    $times = array();
    // Loop thru all diffs
    foreach ($diffs as $interval => $value) {
      // Break if we have needed precission
      if ($count >= $precision) {
 break;
      }
      // Add value and interval 
      // if value is bigger than 0
      if ($value > 0) {
 // Add s if value is not 1
 if ($value != 1) {
   $interval .= "s";
 }
 // Add value and interval to times array
 $times[] = $value . " " . $interval;
 $count++;
      }
    }
    // Return string with times
    return implode(", ", $times);
  }
?>