PHP: How to use the Twitter API's data to convert URLs, mentions, and hastags in tweets to links?

I'm really stumped on how Twitter expects users of its API to convert the plaintext tweets it sends to properly linked HTML.

Here's the deal: Twitter's JSON API sends this set of information back when you request the detailed data for a tweet:

{
    "created_at":"Wed Jul 18 01:03:31 +0000 2012",
    "id":225395341250412544,
    "id_str":"225395341250412544",
    "text":"This is a test tweet. #boring @nbc http://t.co/LUfDreY6 #skronk @crux http://t.co/VpuMlaDs @twitter",
    "source":"web",
    "truncated":false,
    "in_reply_to_status_id":null,
    "in_reply_to_status_id_str":null,
    "in_reply_to_user_id":null,
    "in_reply_to_user_id_str":null,
    "in_reply_to_screen_name":null,
    "user": <REDACTED>,
    "geo":null,
    "coordinates":null,
    "place":null,
    "contributors":null,
    "retweet_count":0,
    "entities":{
        "hashtags":[
            {
                "text":"boring",
                "indices":[22,29]
            },
            {
                "text":"skronk",
                "indices":[56,63]
            }
        ],
        "urls":[
            {
                "url":"http://t.co/LUfDreY6",
                "expanded_url":"http://www.twitter.com",
                "display_url":"twitter.com",
                "indices":[35,55]
            },
            {
                "url":"http://t.co/VpuMlaDs",
                "expanded_url":"http://www.example.com",
                "display_url":"example.com",
                "indices":[70,90]
            }
        ],
        "user_mentions":[
            {
                "screen_name":"nbc",
                "name":"NBC",
                "id":26585095,
                "id_str":"26585095",
                "indices":[30,34]
            },
            {
                "screen_name":"crux",
                "name":"Z. D. Smith",
                "id":407213,
                "id_str":"407213",
                "indices":[64,69]
            },
            {
                "screen_name":"twitter",
                "name":"Twitter",
                "id":783214,
                "id_str":"783214",
                "indices":[91,99]
            }
        ]
    },
    "favorited":false,
    "retweeted":false,
    "possibly_sensitive":false
}

The interesting parts, for this question, are the text element and the entries in the hashtags, user_mentions, and urls arrays. Twitter is telling us where in the text element the hastags, mentions, and urls appear with the indices arrays... so here's the crux of the question:

How do you use those indices arrays?

You can't just use them straight up by looping over each link element with something like substr_replace, since replacing the first link element in the text will invalidate all the index values for subsequent link elements. You also can't use substr_replace's array functionality, since it only works when you give it an array of strings for the first arg, rather than a single string (I've tested this. The results are... strange).

Is there some function that can simultaneously replace multiple index-delimited substrings in a single string with different replacement strings?