Allowing videos to be embedded into comments/text

How does wordpress allow you to embed youtube/dailymotion/vimeo videos by just the url? For example if you type in [youtube=http://www.youtube.com/watch?v=cXXm696UbKY], the video will appear embedded there. Is there anyway t开发者_运维技巧o do this safely in php using markdown?

Most (all?) of this video platforms provide oEmbed support.

For example for the YouTube video http://www.youtube.com/watch?v=cXXm696UbKY it is http://www.youtube.com/oembed?url=http%3A//www.youtube.com/watch%3Fv%cXXm696UbKY.

This will return a response which you can easily parse with json_decode.

{
    "provider_url": "http:\/\/www.youtube.com\/",
    "title": "Auto-Tune the News #8: dragons. geese. Michael Vick. (ft. T-Pain)",
    "html": "<object width=\"425\" height=\"344\"><param name=\"movie\" value=\"http:\/\/www.youtube.com\/v\/bDOYN-6gdRE?fs=1\"><\/param><param name=\"allowFullScreen\" value=\"true\"><\/param><param name=\"allowscriptaccess\" value=\"always\"><\/param><embed src=\"http:\/\/www.youtube.com\/v\/bDOYN-6gdRE?fs=1\" type=\"application\/x-shockwave-flash\" width=\"425\" height=\"344\" allowscriptaccess=\"always\" allowfullscreen=\"true\"><\/embed><\/object>",
    "author_name": "schmoyoho",
    "height": 344,
    "thumbnail_width": 480,
    "width": 425,
    "version": "1.0",
    "author_url": "http:\/\/www.youtube.com\/user\/schmoyoho",
    "provider_name": "YouTube",
    "thumbnail_url": "http:\/\/i3.ytimg.com\/vi\/bDOYN-6gdRE\/hqdefault.jpg",
    "type": "video",
    "thumbnail_height": 360
}

The interesting part is the html property.

So all we have to do is search the text for the [YouTube=...] tag, extract the YouTube URL and retrieve the embed code via oEmbed.

Here a working example:

<?php
function getYouTubeCode($url)
{
    $oembedUrl = 'http://www.youtube.com/oembed?url=' . urlencode($url);

    // The @-operator suppresses errors if the YouTube oEmbed service can't handle our request
    $data = @file_get_contents($oembedUrl);

    // If $data contains invalid JSON code, it will return null
    $data = json_decode($data);

    // So if $data is not an object now, we abort
    if (!is_object($data)) {
        return '';
    }

    // Otherwise we return the YouTube embed code
    return $data->html;
}

$text = '<h1>Hi There</h1><p>You gotta watch this video:</p><p>[YouTube=http://www.youtube.com/watch?v=cXXm696UbKY]</p>';

$matches = array();

// We scan the $text variable for all occurrences of "[YouTube=<Any character except right squared bracket>]"
if (preg_match_all('/\[YouTube=([^\]]+)\]/i', $text, $matches, PREG_SET_ORDER)) {
    foreach ($matches as $match) {
        // Eg. $match[0] is "[YouTube=http://www.youtube.com/watch?v=cXXm696UbKY]"
        // and $match[1] is "http://www.youtube.com/watch?v=cXXm696UbKY"
        $text = str_replace($match[0], getYouTubeCode($match[1]), $text);
    }
}

echo $text;

I really don't know the issue with wordpress, but the basic logic is to search for url and turn it to Youtube embed code, add the stuff around it! I think preg_replace() is what you have to keep in mind!