Need help with preg_replace interpreting {variables} with parameters - php

Question

I want to replace
{youtube}Video_ID_Here{/youtube}
with the embed code for a youtube video.
So far I have
preg_replace('/{youtube}(.*){\/youtube}/iU',...)
and it works just fine.
But now I'd like to be able to interpret parameters like height, width, etc. So could I have one regex for this whether is does or doesn't have parameters? It should be able to inperpret all of these below...
{youtube height="200px" width="150px" color1="#eee" color2="rgba(0,0,0,0.5)"}Video_ID_Here{/youtube}
{youtube height="200px"}Video_ID_Here{/youtube}
{youtube}Video_ID_Here{/youtube}
{youtube width="150px" showborder="1"}Video_ID_Here{/youtube}

Answer 1

Try this:
function createEmbed($videoID, $params)
{
// $videoID contains the videoID between {youtube}...{/youtube}
// $params is an array of key value pairs such as height => 200px
return 'HTML...'; // embed code
}
if (preg_match_all('/\{youtube(.*?)\}(.+?)\{\/youtube\}/', $string, $matches)) {
foreach ($matches[0] as $index => $youtubeTag) {
$params = array();
// break out the attributes
if (preg_match_all('/\s([a-z0-9]+)="([^\s]+?)"/', $matches[1][$index], $rawParams)) {
for ($x = 0; $x < count($rawParams[0]); $x++) {
$params[$rawParams[1][$x]] = $rawParams[2][$x];
}
}
// replace {youtube}...{/youtube} with embed code
$string = str_replace($youtubeTag, createEmbed($matches[2][$index], $params), $string);
}
}
this code matches the {youtube}...{/youtube} tags first and then splits out the attributes into an array, passing both them (as key/value pairs) and the video ID to a function. Just fill in the function definition to make it validate the params you want to support and build up the appropriate HTML code.

Answer 2

You probably want to use preg_replace_callback, as the replacing can get quite convoluted otherwise.
preg_replace_callback('/{youtube(.*)}(.*){\/youtube}/iU',...)
And in your callback, check $match[1] for something like the /(width|showborder|height|color1)="([^"]+)"/i pattern. A simple preg_match_all inside a preg_replace_callback keeps all portions nice & tidy and above all legible.

Answer 3

I would do it something like this:
preg_match_all("/{youtube(.*?)}(.*?){\/youtube}/is", $content, $matches);
for($i=0;$i<count($matches[0]);$i++)
{
$params = $matches[1][$i];
$youtubeurl = $matches[2][$i];
$paramsout = array();
if(preg_match("/height\s*=\s*('|\")([0-9]+px)('|\")/i", $params, $match)
{
$paramsout[] = "height=\"{$match[2]}\"";
}
//process others
//setup new code
$tagcode = "<object ..." . implode(" ", $paramsout) ."... >"; //I don't know what the code is to display a youtube video
//replace original tag
$content = str_replace($matches[0][$i], $tagcode, $content);
}
You could just look for params after "{youtube" and before "}" but you open yourself up to XSS problems. The best way would be look for a specific number of parameters and verify them. Don't allow things like < and > to be passed inside your tags as someone could put do_something_nasty(); or something.

Answer 4

I'd not use regex at all, since they are notoriously bad at parsing markup.
Since your input format is so close to HTML/XML in the first place, I'd rely on that
$tests = array(
'{youtube height="200px" width="150px" color1="#eee" color2="rgba(0,0,0,0.5)"}Video_ID_Here{/youtube}'
, '{youtube height="200px"}Video_ID_Here{/youtube}'
, '{youtube}Video_ID_Here{/youtube}'
, '{youtube width="150px" showborder="1"}Video_ID_Here{/youtube}'
, '{YOUTUBE width="150px" showborder="1"}Video_ID_Here{/youtube}' // deliberately invalid
);
echo '<pre>';
foreach ( $tests as $test )
{
try {
$youtube = SimpleXMLYoutubeElement::fromUserInput( $test );
print_r( $youtube );
}
catch ( Exception $e )
{
echo $e->getMessage() . PHP_EOL;
}
}
echo '</pre>';
class SimpleXMLYoutubeElement extends SimpleXMLElement
{
public static function fromUserInput( $code )
{
$xml = #simplexml_load_string(
str_replace( array( '{', '}' ), array( '<', '>' ), strip_tags( $code ) ), __CLASS__
);
if ( !$xml || 'youtube' != $xml->getName() )
{
throw new Exception( 'Invalid youtube element' );
}
return $xml;
}
public function toEmbedCode()
{
// write code to convert this to proper embode code
}
}