字符串操作，删除一个逗号

Question

UPDATE 1:

This is how I am attempting to build the string:

header('Content-type:application/json');

function getdata($the_query)
{
    $connection = mysql_connect('server', 'user', 'pass') or die (mysql_error());
    $db = mysql_select_db('db_name', $connection) or die (mysql_error());

    $results = mysql_query($the_query) or die(mysql_error());

    $the_data = "{
            \"rss\": {
                \"channels\" : [
                    { 
                        \"title\" : \"".$title."\",
                        \"link\": \"http://www.mycompany.com/external.php\",
                        \"description\": \"company description goes here\",";

                        while($row = mysql_fetch_array($results))
                        {
                            extract($row);

                            $the_data .= "\"items\" : [
                                {
                                    \"title\": \"".$title."\",
                                    \"link\": \"".$link."\",
                                    \"guid\": \"".$link."\",
                                    \"pubDate\": \"".$date."\",
                                    \"description\": \"".$description."\"
                                } ],";
                        }   

                    $the_data .= "} ]
                }
                 }";

    mysql_close($connection);

    return $the_data;
}

ORIGINAL QUESTION:

I have a string similar to this:

$mystring = "{
      \"rss\": {
        \"channels\" : [
          { 
            \"title" : \"title goes here\",
            \"link": \"link goes here\",
            \"description": \"description goes here\",
            \"items\" : [
              {
                \"title\": \"title goes here\",
                \"link\": \"url goes here\",
                \"guid\": \"id goes here\",
                \"pubDate\": \"data goes her\",
                \"description\": \"description goes here\"
              } ],
            \"items\" : [
              {
                \"title\": \"title goes here\",
                \"link\": \"url goes here\",
                \"guid\": \"id goes here\",
                \"pubDate\": \"data goes her\",
                \"description\": \"description goes here\"
              } ],
            \"items\" : [
              {
                \"title\": \"title goes here\",
                \"link\": \"url goes here\",
                \"guid\": \"id goes here\",
                \"pubDate\": \"data goes her\",
                \"description\": \"description goes here\"
              } ],
         } ]
      }
    }";

How do I remove the last comma?

Answer 1

Instead of fixing the error you should fix the cause and don’t insert that last comma in the first place.

The best would be to build the data structure using PHP’s native data types and then use json_encode to convert it to a JSON data string:

function getdata($the_query)
{
    $connection = mysql_connect('server', 'user', 'pass') or die (mysql_error());
    $db = mysql_select_db('db_name', $connection) or die (mysql_error());

    $results = mysql_query($the_query) or die(mysql_error());
    $channel = array(
        'title'       => $title,
        'link'        => 'http://www.example.com/external.php',
        'description' => 'company description goes here',
        'items'       => array()
    );
    while ($row = mysql_fetch_array($results)) {
        $channel['items'][] = array(
            'title'       => $row['title'],
            'link'        => $row['link'],
            'guid'        => $row['link'],
            'pubDate'     => $row['date'],
            'description' => $row['description']
        );
    }
    mysql_close($connection);
    $data = array('rss' => array('channels' => array($channel)));
    return json_encode($data);
}