id in where子句未定义的索引

Question

I'm trying to append some data into an array if it has an id of another table, however I'm getting this:

Undefined index: id

This is my code:

$sql = mysqli_query($mysqli, 'SELECT * FROM users');
$rows = [];

while ($r = mysqli_fetch_assoc($sql)) {
    $rows[] = $r;
    $sql2 = mysqli_query($mysqli, "SELECT * FROM skills WHERE id = '" . $rows['id'] . "'");
    while($r2 = mysql_fetch_assoc($sql2)) {
        $rows[]['skills'] = $r2;
    }
}


print(json_encode($rows));

This part is where I'm having trouble at:

$sql2 = mysqli_query($mysqli, "SELECT * FROM skills WHERE id = '" . $rows['id'] . "'");
while($r2 = mysql_fetch_assoc($sql2)) {
    $rows[]['skills'] = $r2;
}

What am I doing wrong?

Answer 1

The code $rows[] = $r means add the value of $r to the end of $rows. So the array becomes:

Array
(
    [0] => Array
        (
            [id] => 1
        )

)

If you want to access the id property, either use $rows[0]['id'] or $r['id'].

EDIT:

Also note that in the code snippet you use mysql_fetch_assoc instead of mysqli_fetch_assoc.