$re = '/https?:\/\/(?:www.)?instagram.com\/reel\/([^\/?#&]+).*/m';
$str = 'https://www.instagram.com/reel/COKwCmxF5rg/?utm_medium=copy_link
https://www.instagram.com/reel/CPmmgosDt5P/?utm_medium=copy_link
https://www.instagram.com/reel/CP3XqlLFnVp/?utm_medium=copy_link
https://www.instagram.com/reel/CQGlAPyoJJQ/?utm_medium=copy_link
https://www.instagram.com/reel/CPvQ3byFP0n/?utm_medium=copy_link
https://www.instagram.com/reel/CQAzj4xjERd/?utm_medium=copy_link
https://www.instagram.com/reel/CQREuNLnk4h/?utm_medium=copy_link
https://www.instagram.com/reel/CPxOWAJATxZ/?utm_medium=copy_link
https://www.instagram.com/reel/CPv2e1ej7Sq/?utm_medium=copy_link
https://www.instagram.com/reel/CP4fkUoBY9q/?utm_medium=copy_link
https://www.instagram.com/reel/CQL2EcVHtMz/?utm_medium=copy_link
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php