origin policy olayını atlatmak pek kolay değil ne yazık ki. dosyayı 1 kereliğine alsan, local de saklayıp kullanıcıya onu sunsan? cron ala arada silersin falan ...

<?php

error_reporting(0);

$url = 'https://scontent.cdninstagram.com/v/t50.2886-16/244392168_894608178139298_4686772010645637206_n.mp4?_nc_ht=instagram.fist4-1.fna.fbcdn.net&_nc_cat=102&_nc_ohc=FcmD_8OecNwAX-7zfEc&edm=AABBvjUBAAAA&ccb=7-4&oe=615EB1F2&oh=1cb6287e70c30216eb9f9e4341f58a82&_nc_sid=83d603';

$localFile = 'temp/'.md5($url).'.mp4';

if(!file_exists($localFile)){
    DownVid($url, $localFile);
}

function DownVid($url, $localFile){
    $ch = curl_init($url);
    curl_setopt_array($ch,
        [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_CONNECTTIMEOUT => 30,
        ]
    );
    $response = curl_exec($ch);
    file_put_contents($localFile, $response);
    curl_close($ch);
    return true;
}

?><!DOCTYPE html>
<html>
<body>
    <video width="320" height="240" controls>
      <source src="<?php echo $localFile ?>" type="video/mp4">
    </video>
</body>
</html>