如何在PHP的while循环内进行if if条件？

Question

I want to make an array that looks like this:

qqq = [[a,b],[c,d]];

But with the code that I got it makes an output that looks like this:

qqq= [[a,b],[c,d],];

what should i do to exclude the extra semicolon?

var qqq = [<?php 
        $aw = "select * from city;";
        $wa = mysql_query($aw);

    while($aa = mysql_fetch_array($wa))
        {       
            $cc = $aa['Coordinate_id'];
            $bb = $aa['city_name'];

            echo "[$cc,$bb],";

        }   
?> ];

Answer 1

Since you are going for a JSON encoded array, please use the following snippet to achieve exactly the same:

var qqq = <?php 
    $aw = "select * from city;";
    $wa = mysql_query($get_marker);

    $arr = array();
    while($aa = mysql_fetch_array($wa)) {
        $arr[] = array($aa['Coordinate_id'], $aa['city_name']);
    }
    echo json_encode($arr);
?>;

Answer 2

Replace this:

while($aa = mysql_fetch_array($wa))
{
    $cc = $aa['Coordinate_id'];
    $bb = $aa['city_name'];
    echo "[$cc,$bb],";
}

to this:

$result = '';
while($aa = mysql_fetch_array($wa))
{
    $cc = $aa['Coordinate_id'];
    $bb = $aa['city_name'];
    result.="[$cc,$bb],";
} 
echo trim($result,',');

Answer 3

Instead of echo you should use implode like this

<?php 
$aw = "select * from city;";
$wa = mysql_query($get_marker);
$arr = [];
while($aa = mysql_fetch_array($wa))
{       
    $cc = $aa['Coordinate_id'];
    $bb = $aa['city_name'];

    $arr[] = "[$cc,$bb]";
}   
?>

var qqq = [<?php echo implode(',',$arr)?>];

I think this improves readability as well and is more easily ported to something more manageable

Answer 4

Count the number of rows:

$num = mysql_num_rows($aw);

And check if the condition applies that the last loop is occurring by using a counter:

$i = 0;
while($aa = mysql_fetch_array($wa))
{       
    $cc = $aa['Coordinate_id'];
    $bb = $aa['city_name'];

    if ($i < $num)
    {
        echo "[$cc,$bb],";
    }
    else
    {
        echo "[$cc,$bb]";
    }
    $i++;
}   

Finally, note that mysql_* functions are deprecated and should be avoided. Use PDO or mysqli instead.

Answer 5

Use an array instead of echo and implode outside while loop

var qqq = [<?php 
    $aw = "select * from city;";
    $wa = mysql_query($get_marker);

$ret = array();

while($aa = mysql_fetch_array($wa))
{       
    $cc = $aa['Coordinate_id'];
    $bb = $aa['city_name'];

    $ret[] = "[$cc,$bb]";

}   

echo implode(',', $ret);
?> ];