如何在PHP中使用JavaScript变量？ [关闭]

Question

I'm making a website that uses a lot of different php files. My site uses Wordpress and is a music blog. I have a jPlayer playlist at the top of the screen and for each individual post I want to have a play button to play that song.

I've made a few functions in php and in javascript across a few different php files. How can I declare a global JavaScript variable in one of my php files and access it in another php file? I know that is worded badly, so let me explain.

File 1: my_functions.php (where I set up my jPlayer playlist. The variable song_index is what I want to be global.

<script type = "text/javascript">
    var song_index = 0;
    var theTitles = new Array();
    var theMP3s = new Array();
    var jplayer_playlist;

    function add_song(title, mp3)
    {
        theTitles[song_index] = title;
        theMP3s[song_index] = mp3;
        song_index++;
    }

    function play_song(index)
    {
        alert("You want to play song " + index);
        //jplayer_playlist.play(index);
    }

    function get_playlist()
    {
        var playlist = new Array();

        for(var i = 0; i < theTitles.length; i++)
        {
            playlist[i] = {title: theTitles[i], mp3: theMP3s[i]};
        }
        return playlist;
    }


    $(document).ready(function()
    {
        var playlist = get_playlist();
        jplayer_playlist = new jPlayerPlaylist({
            jPlayer: "#jquery_jplayer_1",
            cssSelectorAncestor: "#jp_container_1",
            oggSupport:false
        }, playlist, {
            swfPath: "/js",
            supplied: "mp3",
            wmode: "window"
        }
        );
    });
    //]]>
    </script>

This sets up my jPlayer playlist dynamically for each page.

File 2 shortcodes.php (this is where I add songs using Wordpress' shortcodes. Here is the code that I use when I want to add a song to the playlist...)

    function player_function($args)
{
    $url = $args['url'];
    $title = $args['title'];

    if(!$title)
    {
        $title = get_the_title();
    }

    add_song($title, $url);

    $ret = "<a href = '" . $url . "'></a><br><a href=\"javascript:void(0)\" onclick = \"play_song(".$_GET['window.song_index'].")\">Play</a>";

    return "$ret";
}

Pretty much I just need to access song_index from the first file into a php variable so I can pass it along. As you can see, I tried using $_GET because someone said you can access JS variables this way, but it didn't work. Anyone have any clues?

Answer 1

Javascript and PHP don't actually know anything about one another. However, you can use PHP to write to JavaScript. So in my_functions.php you could do this:

<?php
  $myGlobalSongIndex = '0'; // or however you want to assign this else....
?>
<script type = "text/javascript">
    var song_index = <?php print myGlobalSongIndex; ?>;

Then in shortcodes.php on the write link line, print $myGlobalSongIndex instead of the $_GET['window.song_index'] that you are doing now. The one thing that you need to make sure of is that $myGlobalSongIndex is in scope in both places. Meaning if it is inside a function or class, you will need to use the global keyword.

There is a downside to this exact approach. You will not be able to separate the javascript into a separate file which can be quite nice in many case. You could write just the following in the php, as part of the html's head section:

<?php
  $myGlobalSongIndex = '0'; // or however you want to assign this else....
?>
<script type = "text/javascript">
    var song_index = <?php print myGlobalSongIndex; ?>;
</script>

And make sure that you load the external javascript file afterwards. Then when you use the song_index in the javascript file, you would probably want to make sure it is indeed initialized for any pages where you may include it without rendering the field in php.