$re = '/\/dp\/([^\/]*)\//';
$str = 'http://www.amazon.in/Sinew-Nutrition-Decaffeinated-Unroasted-Management/dp/B01LF7Y0S4/ref=sr_1_1?ie=UTF8&qid=1484716249&sr=8-1&keywords=green+coffee+beans';
preg_match_all($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