$re = '/wpsite\.com\/wp-json\/wp\/v2\/posts\?tags\[]=6287&tags\[]=6289&_fields/m';
$str = 'https://wpsite.com/wp-json/wp/v2/posts?tags[]=6287&tags[]=6289&_fields=jetpack_featured_media_url,title.rendered,excerpt.rendered,link,id&per_page=100&page=1&orderby=date';
preg_match_all($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