How to Convert Youtube Data API V3 video duration format to seconds in PHP?

We get the youTube Video duration in below way from Youtube V3 API.

 "contentDetails": {
    "duration": "PT15S",
    "dimension": "2d",
    "definition": "sd",
    "caption": "false",
    "licensedContent": true,
    "projection": "rectangular"
   },

Now, We need to convert the duration to number of seconds.
Following are Simple PHP Function which convert the API V3 video duration format to number of seconds.

 function duration($ytDuration) {
    $di = new DateInterval($ytDuration);
    
    $totalSec = 0;
    if ($di->h > 0) {
      $totalSec+=$di->h*3600;
    }
    if ($di->i > 0) {
      $totalSec+=$di->i*60;
    }
    $totalSec+=$di->s;
    
    return $totalSec;
  }
$youtubeTime = 'PT15S';
 echo duration($youtubeTime);//15
 
 
$youtubeTime = 'PT2M55S'; 
echo duration($youtubeTime);//175

$youtubeTime = 'PT1H35M23S'; 
echo duration($youtubeTime);//5723