mysql - Removing Last Comma within while loop - PHP

Question

I've been building a little tool to manage a dataset, I'm trying create a JSON output in order to serve my front-end the data.

Right now I have an extra comma at the end of every row in the loop. I need to remove it, it would be ideal if I can find a way to do this inside of the while loop.

Here is my code:

$sth = mysql_query("SELECT * FROM mapdata");
$num_rows = mysql_num_rows($sth);
$counter = 0;
echo '[';
while($r = mysql_fetch_assoc($sth)) {
    if (++$counter == $num_rows) {
        echo json_encode($r) . '';
    }
    else {
        echo json_encode($r) . ',';
    }
}
echo "]";
mysql_close($connection);

This is what I'm getting returned now

[
{"col1":"123","col2":"456","col3":"789",},
{"col1":"123","col2":"456","col3":"789",}
]

This is what I need.

[
{"col1":"data1","col2":"data2","col3":"data3"},
{"col1":"data1","col2":"data2","col3":"data3"}
]

Any suggestions would be greatly appreciated.

Answer 1

Your whole approach is wrong, you shouldn't try to create JSON by hand. Put all the rows in an array, and let json_encode() do it all for you.

$result = array();
while ($r = mysql_fetch_assoc($sth)) {
    $result[] = $r;
}
echo json_encode($result);