从php代码内部执行shell脚本

我想做的是使用php执行youtube-dl -x --audio-format mp3 "token"，并获得以下参数的json：

• 状态（错误=0/成功=1）
• 保存的文件url（您将在控制台结果示例中看到它：[avconv] Destination: Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.mp3）

这是我写的PHP代码。

<?php
if ($_GET["token"]) {
            $url =  $_GET["token"];
            $template = '/home/website/public_html/%(id)s.%(ext)s';
            $string = ('youtube-dl -x --audio-format mp3 ' . escapeshellarg($url) . ' ' . escapeshellarg($template));
            $descriptorspec = array(
                0 => array("pipe", "r"),  // stdin
                1 => array("pipe", "w"),  // stdout
                2 => array("pipe", "w"),  // stderr
            );
            $process = proc_open($string, $descriptorspec, $pipes);
            $stdout = stream_get_contents($pipes[1]);
            fclose($pipes[1]);
            $stderr = stream_get_contents($pipes[2]);
            fclose($pipes[2]);
            $ret = proc_close($process);
            echo json_encode(array('status' => $ret, 'errors' => $stderr,
                'url_orginal' => $url, 'output' => $stdout,
                'command' => $string));
        }
?>

基本上它执行

youtube-dl -x --audio-format mp3 "token"

当我在控制台中（通过SSH）执行相同的命令时，我会得到类似的结果

[youtube] Setting language
[youtube] Confirming age
[youtube] nxtIRArhVD4: Downloading webpage
[youtube] nxtIRArhVD4: Downloading video info webpage
[youtube] nxtIRArhVD4: Extracting video information
[youtube] nxtIRArhVD4: Encrypted signatures detected.
[youtube] nxtIRArhVD4: Downloading js player vflE7vgXe
[download] Destination: Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.m4a
[download] 100% of 3.93MiB in 00:00
[avconv] Destination: Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.mp3
Deleting original file Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.m4a (pass -k to keep)

当我在php环境中执行相同的命令时，得到以下json结果

    {
   "status":1,
   "errors":"WARNING: The url doesn't specify the protocol, trying with http'nWARNING: Could not send HEAD request to http:'/'/'/home'/website'/public_html'/%(id)s.%(ext)s: 'nWARNING: Falling back on generic information extractor.'nERROR: Unable to download webpage: 'n",
   "url_orginal":"nxtIRArhVD4",
   "output":"[youtube] Setting language'n[youtube] Confirming age'n[youtube] nxtIRArhVD4: Downloading webpage'n[youtube] nxtIRArhVD4: Downloading video info webpage'n[youtube] nxtIRArhVD4: Extracting video information'n[youtube] nxtIRArhVD4: Encrypted signatures detected.'n[youtube] nxtIRArhVD4: Downloading js player vflE7vgXe'n[download] Destination: Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.m4a'n'r[download] 0.0% of 3.93MiB at 729.44KiB'/s ETA 00:05'r[download] 0.1% of 3.93MiB at 1.86MiB'/s ETA 00:02'r[download] 0.2% of 3.93MiB at 3.86MiB'/s ETA 00:01'r[download] 0.4% of 3.93MiB at 7.69MiB'/s ETA 00:00'r[download] 0.8% of 3.93MiB at 13.79MiB'/s ETA 00:00'r[download] 1.6% of 3.93MiB at 17.80MiB'/s ETA 00:00'r[download] 3.2% of 3.93MiB at 17.64MiB'/s ETA 00:00'r[download] 6.3% of 3.93MiB at 17.79MiB'/s ETA 00:00'r[download] 12.7% of 3.93MiB at 20.88MiB'/s ETA 00:00'r[download] 25.4% of 3.93MiB at 25.21MiB'/s ETA 00:00'r[download] 50.8% of 3.93MiB at 28.47MiB'/s ETA 00:00'r[download] 100.0% of 3.93MiB at 41.23MiB'/s ETA 00:00'r[download] 100% of 3.93MiB in 00:00'n[avconv] Destination: Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.mp3'nDeleting original file Jennifer Lopez - Booty ft. Iggy Azalea-nxtIRArhVD4.m4a (pass -k to keep)'n[generic] %(id)s: Requesting header'n[generic] %(id)s: Downloading webpage'n",
   "command":"youtube-dl --extract-audio --audio-format mp3 'nxtIRArhVD4' ''/home'/website'/public_html'/%(id)s.%(ext)s'"
}

事实上php做工作并保存文件，但输出不一样，我无法获得目标文件的url。

我做错了什么？有什么建议吗？