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.

Why are you doing it like this? Why don't you just put everything into an array and call `json_encode()` on the whole thing? — Barmar, Sep 05 '14 at 00:32
I don't see where that extra comma is coming from. `json_encode($r)` doesn't add an extra comma like that. — Barmar, Sep 05 '14 at 00:34
@Barmar it's being appended in the else section of the statement — Daryl Gill, Sep 05 '14 at 00:35
No it isn't. That's the comma AFTER the `}`, his problem is the comma BEFORE the `}`. — Barmar, Sep 05 '14 at 00:36
@Ghost That's what I said in the first comment. I just posted an answer showing how to do it. — Barmar, Sep 05 '14 at 00:40
@Barmar yeah, i was the one who upvoted, that should be the right way — Kevin, Sep 05 '14 at 00:41
https://stackoverflow.com/questions/1642698/how-do-i-remove-a-comma-off-the-end-of-a-string : $string = rtrim($string, ','); — FreudianSlip, May 16 '18 at 11:01

score 6 · Answer 1 · answered Sep 05 '14 at 00:38

6

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);

answered Sep 05 '14 at 00:38

Barmar

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score 0 · Accepted Answer · answered Sep 09 '14 at 04:10

I like to follow best practice whereever possible, but in this particular instance I needed to deviate from best practice due to some environment restrictions I had. I thought I'd share the solution I ended up using, regardless of it being overly complicated.

$sth = mysql_query("SELECT name,address,address2,city,state,postal,phone,lat,lng FROM mapdata");
$num_rows = mysql_num_rows($sth);
$counter = 0;
echo '[';
while($r = mysql_fetch_assoc($sth)) {
    if (++$counter == $num_rows) {
        echo preg_replace("/^,/",'',str_replace(',}','}',json_encode($r)));

    }
    else {
        echo preg_replace("/^,/",'',str_replace(',}','}',json_encode($r)) . ',');
    }
}
echo "]";
mysql_close($connection);

Removing Last Comma within while loop - PHP

2 Answers2

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