PHP function that turns vimeo and youtube urls in to videos.

functions.php

<?php  
  function filter_video_links( $content ){
    
    	// Regular Expressions
  		$youtube_link = '@^\s*https?://(?:www\.)?(?:youtube.com/watch\?|youtu.be/)([^\s"]+)\s*$@im';
  		$vimeo_link = '@^\s*https?://(?:www\.)?(?:vimeo.com/)@im';
  
  		if( preg_match( $vimeo_link, $content ) ) {
  			// vimeo
  			$content = preg_replace( $vimeo_link, 'http://player.vimeo.com/video/', $content );
  			return $content;
  
  		} else if ( preg_match( $youtube_link, $content ) ) {
  			// youtube
  			$content = str_replace( 'http://www.youtube.com/watch?v=', 'http://www.youtube.com/embed/', $content );
  			return $content;
        
  		} else {
  			return $content;
      }
  
  	}
?>