<?php 
$apiKey = "AIzaSyB-8Rgov8Qp1uIw40Bi2_1spqgm-asQCmo";  //Api key
$videoid = "C2oROu5rZcM"; //Youtube Video ID'si
$dataUrl = "https://www.googleapis.com/youtube/v3/videos?id=".$videoid."&part=contentDetails&key=".$apiKey;

$Baglan = file_get_contents($dataUrl);
$jData = json_decode($Baglan);
$sure  = $jData->items[0]->contentDetails->duration;

function sure_cevir($sure){
	$saat = strpos($sure,"H");
	$dk = strpos($sure,"M");
	if($saat > 0){ //Saat varsa
	preg_match('#PT(.*?)H(.*?)M(.*?)S#',$sure,$tamsaat);
	$tamsaat = $tamsaat[1].":0".$tamsaat[2].":".$tamsaat[3];
	}else if($dk > 0 && $saat == 0){ //Dk varsa
		preg_match('#PT(.*?)M(.*?)S#',$sure,$tamsaat);
		$tamsaat = $tamsaat[1].":".$tamsaat[2];
	}else{
		preg_match('#PT(.*?)S#',$sure,$tamsaat);
		$tamsaat = "0:".$tamsaat[1];
	}
	return $tamsaat;
}
echo sure_cevir($sure);
// print_r($tamsure);