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Re: Extracting multiple matches from a string using preg_replace

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On Mon, 9 Jul 2012 01:50:39 -0700 (PDT), Jason C wrote:

> I'm working with a message board database that already has a bunch of
> YouTube links in the comments, and I'm trying to replace all of the
> links with a new alternate.
>
> The existing strings are like:
>
> $this_comment = '<a href="http://www.youtube.com/watch?v=vidid"
> target="_new">http://www.youtube.com/watc...vidid</a><br><br><a
> href="http://www.youtube.com/watch?v=vidid_2"
> target="_new">http://www.youtube.com/watc...vidid_2</a>';
>
> Notice that this string has 2 separate YouTube links.
>
> If you're not familiar, YouTube has several possible link formats, so
> using parse_url() doesn't really work:
>
> youtube.com/v/{vidid}
> youtube.com/vi/{vidid}
> youtube.com/?v={vidid}
> youtube.com/?vi={vidid}
> youtube.com/watch?v={vidid}
> youtube.com/watch?vi={vidid}
> youtu.be/{vidid}
> youtube.com/v/{vidid}?feature=autoshare&version=3&autohide=1&autoplay=1
>
>
> I've written the regex to find the ID and replace the link correctly,
> but it only works with the first link that it finds. How do I make it
> work with all of the matching links in the string?

That's the drawback to using preg_replace() for this. You can't capture
all the bits you want to extract because you *must* enumerate them.
preg_match_all() returns an array of matches, which is what you want if
you don't know how many you're going to get back going in.

> Here's what I have:
>
> // Fetch the VIDID $this_id = preg_replace("#.*?<a
> href=\"http://.*?youtu\.*?be[\.com]*/[watch]*[\?]*(v/|v=|vi/|vi=)*(.*?
> )[&.+]*\" target=\"_new\">.*?<\/a>.*#", "$2", $this_comment);
                                           ^^ -- enumerated result
>
> // I'm not sure why preg_replace isn't catching the extra variables;
> // I thought the [&.+]* would do this? Either way, this is a
> workaround: list($this_id) = explode("&", $this_id);

Define "catching" in this context. If you want it back, you need to
paren-tag it so it goes into an enumerated output slot.

> // Replace link if ($this_id) { $new_link = "Example replacement:
> $this_id";
>
>   $this_comment = preg_replace("#<a
> href=\"http://.*?youtu\.*?be[\.com]*/[watch]*[\?]*(v/|v=|vi/|vi=)*"
> . $this_id . "[&.+]*\" target=\"_new\">.*?<\/a>#", "$new_link",
> $this_comment); }


-- 
"'I'm not sleeping with a jr. high schooler! I have a life-sized doll
that looks like one.' Uh huh. That sounds SO much less pathetic." 
                 -- Piro's Conscience  www.megatokyo.com

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Thread

Extracting multiple matches from a string using preg_replace Jason C <jwcarlton@gmail.com> - 2012-07-09 01:50 -0700
  Re: Extracting multiple matches from a string using preg_replace Captain Paralytic <paul_lautman@yahoo.com> - 2012-07-09 05:44 -0700
    Re: Extracting multiple matches from a string using preg_replace Jason C <jwcarlton@gmail.com> - 2012-07-09 11:58 -0700
  Re: Extracting multiple matches from a string using preg_replace "Peter H. Coffin" <hellsop@ninehells.com> - 2012-07-09 08:29 -0500
    Re: Extracting multiple matches from a string using preg_replace Jason C <jwcarlton@gmail.com> - 2012-07-09 12:00 -0700
    Re: Extracting multiple matches from a string using preg_replace Jason C <jwcarlton@gmail.com> - 2012-07-10 02:08 -0700

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