Replacing Placeholder text containing a variable

Question

Hi I have placeholder text in my content from the CMS like this:

$content = "blah blah blah.. yadda yadda, listen to this:
{mediafile file=audiofile7.mp3}
and whilst your here , check this: {mediafile file=audiofile24.mp3}"

and i need to replace the placeholders with some html to display the swf object to play the mp3.
How do i do a replace that gets the filename from my placeholder.

I think the regx pattern is {mediafile file=[A-Za-z0-9_]} but then how do i apply that to the whole variable containing the markers?

Thanks very much to anyone that can help,

Will

Answer 1

Read the regex docs carefully.

your pattern looks a little off. {mediafile file=([^}]+)} might be ore like what you're looking for (the regex you gave doesn't allow for ".").

Answer 2

you do something like that

$content = preg_replace_callback(
        '|{mediafile file='([A-Za-z0-9_.]+)}|',
        create_function(
            // single quotes are essential here,
            // or alternative escape all $ as \$
            '$matches',
            'return "<embed etc ... " . ($matches[1]) ."more tags";'
        ),
        $content
    );

you can see the manual of preg_replace_callback. Normal preg_replace also work but might be a messy.

Answer 3

Hi,

Here is a quick example, using preg_replace_all, to show how it works :

if $content is declared this way :

$content = "blah blah blah.. {mediafile file=img.jpg}yadda yadda, listen to this:
{mediafile file=audiofile7.mp3}
and whilst your here , check this: {mediafile file=audiofile24.mp3}";

You can replace the placeholders with something like this :

$new_content = preg_replace_callback('/\{mediafile(.*?)\}/', 'my_callback', $content);
var_dump($new_content);

And the callback function might look like this :

function my_callback($matches) {
    $file_full = trim($matches[1]);
    var_dump($file_full);       // string 'file=audiofile7.mp3' (length=19)
                                // or string 'file=audiofile24.mp3' (length=20)
    $file = str_replace('file=', '', $file_full);
    var_dump($file);            // audiofile7.mp3 or audiofile24.mp3

    if (substr($file, -4) == '.mp3') {
        return '<SWF TAG FOR #' . htmlspecialchars($file) . '#>';
    } else if (substr($file, -4) == '.jpg') {
        return '<img src="' . htmlspecialchars($file) . '" />';
    }
}

Here, the last var_dump will get you :

string 'blah blah blah.. <img src="img.jpg" />yadda yadda, listen to this:
<SWF TAG FOR #audiofile7.mp3#>
and whilst your here , check this: <SWF TAG FOR #audiofile24.mp3#>' (length=164)

Hope this helps :-)

Don't forget to add checks and all that, of course ! And your callback function will most certainly become a bit more complicated ^^ but this should give you an idea of what is possible.

BTW : you might want to use create_function to create an anonymous function... But I don't like that : you've got to escape stuff, there is no syntax-highlighting in the IDE, ... It's hell with a big/complex function.

Answer 4

I originally was thinking you could use a function that involved json_decode, but strings need to be wrapped in quotes or json_decode doesn't handle them. So if your placeholders were written:

{"mediafile" : "file" : "blahblah.mp3"}

you could change my sample code from using explode($song) to json_decode($song, true) and have a nice keyed array to work with.

Either way, I went with using the strtok function to find the placeholders, and then a basic string replace function to change the instances of the found placeholders into html, which is just gibberish.

strtok, so far as PHP docs indicate, does not use regex, so this would be not only simpler but also avoid a call to the preg library.

One last thing. If you do go with json syntax, you will have to re-wrap the placeholders in{} as strtok removes the tokens it is searching by.

<?php
$content = "blah blah blah.. yadda yadda, listen to this:
{mediafile file=audiofile7.mp3}
and whilst your here , check this: {mediafile file=audiofile24.mp3}";

    function song2html($song) {
       $song_info = explode("=", $song);
       $song_url = $song_info[1];
       $song_html = "<object src=\"$song_url\" blahblahblah>blah</object>";
    return ($song_html);
    }

$tok = strtok($content, "{}");

while ($tok !== false) {
    if(strpos($tok, "mediafile") !== false) {
  $songs[] = $tok;
 }
 $tok = strtok("{}");
}

foreach($songs as $asong) {
 $content = str_replace($asong, song2html($asong), $content);
}

echo $content;
?>