- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$blogPostWord = 'www.youtube.com/watch?v=VePkkkM9XBA';
preg_match('#(?<=(?:v|i)=)[a-zA-Z0-9-]+(?=&)|(?<=(?:v|i)\/)[^&\n]+|(?<=embed\/)[^"&\n]+|(?<=(?:v|i)=)[^&\n]+|(?<=youtu.be\/)[^&\n]+#', $blogPostWord, $matches);
var_dump($matches);