<?php
$link= 'https://www.tiktok.com/@philandmore/video/6805867805452324102';
$sayi = preg_replace( '/[^0-9]/', '', $link );

var link = 'https://www.tiktok.com/@philandmore/video/6805867805452324102';
var pattern = /\d+/g;
var sayi = link.match(pattern).join('');