PHP next($array) moves pointer only once

Question

I am new to PHP and am working currently on this web page that reads a number of audio files in a folder and lets the user write a transcript about what she/he had heard. At the moment i can read files in a directory and shuffle that array. I also wanted to implement two buttons that would let the user listen to the next/previous files. That is where i am having problems right now. The next button seems to be working but not as i would like. The problem is that i can move the pointer just once. I mean i can just from the first file to the second and i can't advance any further. Here is my code for the function that is called when the user clicks on the button: function nextelem(){

            var nextElement = "./Sound data/<?php


            $current_id = current($files);
            $current_index = array_search($current_id, $files);     
            $next_index = $current_index+1;

            echo $files[$next_index];

            next($files);

            ?>";

            //Play the next file
            document.getElementById('RandomAudio').src=nextElement;


          }

I'm guessing that the problem is that current($array) and next($array) functions work by the by-value principle and so every time the function is being called, a copy of the original array is passed so everytime the button is clicked i get the first element as the current and moving the pointer with next($array) doesn't really have an effect.

So i tried writing my own current($array) and next($array) functions:

        <?php
               function &current_by_ref(&$arr) {
                    return $arr[key($arr)];
                }
                function &next_by_ref(&$arr) {
                    return $arr[key($arr)+1];
                }
        ?>;

but these did not help either. I would really appreciate any help or tips. This is starting to get to my nerves. (PS: I opened a topic about (the same project but not the same problem) and that was really helpful. the link is here PHP next($array) and Javascript . I posted all of the code there, it is not the last version i am working on right now but it can give you more of an idea about the page i think. so thanks anyway)

based on freon's answer i changed to code to :

               session_start();
                $dir = './Sound data';
                $files = scandir($dir); 


                    $norp = $_GET['name'];  

                    $current_id = current($files);
                    $current_index = array_search($current_id, $files);     
                    $_SESSION['current'] = $current_index;
                    $_SESSION['songlist'] = $files;

                    $current_song = $_SESSION['current']; //index in songlist for your song
                    $songlist = $_SESSION['songlist']; //this session var has your $files array
                    if($norp == 'nextS'){

                        $current_song++; //changes currentsong to next song
                        if($current_song == count($songlist))
                           $current_song = 0;
                        echo "./Sound data/$songlist[$current_song]";
        }           

                    else if($norp == 'prevS'){
                        $current_song--;     //changes currentsong to prev song

                        if($current_song == count($songlist))
                        $current_song = 0;
                        echo "./Sound data/$songlist[$current_song]";
                    }

?>

and

    <script language="JavaScript" type="text/javascript" >

        function getNextSong()
        {                 
            $.get('getsong.php', {name : 'nextS'}, function(song){

                document.getElementById('RandomAudio').src =  song;
                document.getElementById('filename').innerHTML= song;
            //  alert(song);
            });
        }

        function getPreviousSong()
        {                 
            $.get('getsong.php', {name : 'prevS'}, function(song){

                document.getElementById('RandomAudio').src =  song;
                document.getElementById('filename').innerHTML= song;
            //  alert(song);
            });
        }
    </script>

but i still can't reach beyond the immediate next element. am i doing something wrong?

I think maybe you need to put some form of loop in there, chief. — Sammitch
– Sammitch, Commented Nov 1, 2012 at 17:14

Matheus Azevedo · Accepted Answer · 2012-11-05 16:53:57Z

2

You're mixing PHP and JavaScript. You can't do that. The code will be interpreted, and you'll have only the next file available. Your output prabably is:

var nextElement = "./Sound data/2.mp3";
   document.getElementById('RandomAudio').src=nextElement;

In the second time you press the button, the same code will be executed. That's why you can't go further. You have to find a way to retrieve from the server the next audio, and for that you must keep track of which audio is beeing played now.

getsong.php

<?php
session_start(); //init session

if(!isset($_SESSION['songlist']) or empty($_SESSION['songlist']))
{ //we'll create our songlist JUST ONCE, when it's not created yet. And then, we'll put this list in a SESSION, so we can access it later.
    $dir = './Sound data';
    $files = scandir($dir);
    $_SESSION['songlist'] = array();
    foreach($files as $file)
    {//loop through song list and just add actual files, disposing "." and ".."
        if(is_file($file) and $file != "." and $file != "..")
        {
            $_SESSION['songlist'][] = $file; //add $file to songlist array.
        }
    }
    shuffle($_SESSION['songlist']);//shuffle list
    $_SESSION['current'] = 0; //iniate current song with first song in the list.
}//note that we'll create and shuffle the song list just once.

$norp = $_GET['name'];

$current_song = $_SESSION['current']; //index in songlist for your song
$songlist = $_SESSION['songlist']; //this session var has your $files array

if($norp == 'nextS'){
    $current_song++; //changes currentsong to next song
    if($current_song == count($songlist)) //if current is after the last element, set it to the first song
        $current_song = 0;
    echo "./Sound data/$songlist[$current_song]";
}
else if($norp == 'prevS'){
    $current_song--;     //changes currentsong to prev song
    if($current_song == -1) //if current is before the fist song, set it to the last song
        $current_song = count($songlist) - 1;

    echo "./Sound data/$songlist[$current_song]";
}

$_SESSION['current'] = $current_song; //store current song for later use.
?>

listensong.php //page that plays your songs (with code optimization)

<script type="text/javascript">
    //using jQuery
    function getSong(type)
    {
        $.get('getsong.php', {name: type}, function(song){
            document.getElementById('RandomAudio').src = song;
            document.getElementById('filename').innerHTML= song;
        });
    }
</script>
<a href="javascript:getSong('prevS')">Previous Song</a>
<a href="javascript:getSong('nextS')">Next Song</a>

edited Nov 5, 2012 at 16:53

answered Nov 1, 2012 at 17:19

Matheus Azevedo

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6 Comments

Revangelis Over a year ago

thanks a lot! this was really helpful. i tried making it this way. the reading of the directory and the shuffling of the array is being done in another .php file and in getsong.php i am including that file. the next button seems to be working but i don't know whether i am shuffling the array everytime i click on 'Next Song' and getting the first element or actually going forward. therefore i wanna ask: is there a way to call a specific function from 'getsong.php'using jquery?

Revangelis Over a year ago

i tried using something like $.get('getsong.php', { nextorprev = 'next' }, function(song){} for the next button and writing an if statement in the getsong.php but i am having difficulty using the passed nextorprev variable in the getsong.php .any tips on how i can do that?

Revangelis Over a year ago

ok i managed to get the passed variable but i found out that i am shuffling the array everytime i click on next and i am listening to the first song.

Revangelis Over a year ago

well i still can't advance beyond 1. i disabled the shuffle and its no good.

Matheus Azevedo Over a year ago

I've changed the answer with the code you need. Please, read it carefully and try to learn what is happening.

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