将数组提取到动态变量中

Question

I am trying to be lazy (or smart): I have 7 checkboxes which correlate with 7 columns in a MySQL table.

The checkboxes are posted in an array:

$can = $_POST['can'];

I've created the following loop to dump the variables for the MySQL insert:

for($i=1;$i<8;$i++){
    if($can[$i] == "on"){
        ${"jto_can".$i} = 'Y';
    }
    else{
        ${"jto_can".$i} = 'N';
    }
}
print_r($jto_can1.$jto_can2.$jto_can3.$jto_can4.$jto_can5.$jto_can6.$jto_can7);

This correctly outputs:

YYNYYYY

However, when I attempt to use those variables in my MySQL update, it doesn't accept the changes.

mysqli_query($db, "UPDATE jto SET jto_can1 = '$jto_can1', jto_can2 = '$jto_can2', jto_can3 = '$jto_can3', jto_can4 = '$jto_can4', jto_can5 = '$jto_can5', jto_can6 = '$jto_can6', jto_can7 = '$jto_can7' WHERE jto_id = '$id'")or die(mysqli_error($db));

Can anyone explain why the print_r displays the variables whereas MySQL update does not?

Answer 1

Stick with the array, and form the query dynamically:

$sql = 'UPDATE jto SET ';

$cols = array();
foreach( range( 1, 7) as $i) {
    $value = $_POST['can'][$i] == 'on' ? 'Y' : 'N'; // Error check here, $_POST['can'] might not exist or be an array
    $cols[] = 'jto_can' . $i . ' = "' . $value . '"'; 
}

$sql .= implode( ', ', $cols) . ' WHERE jto_id = "' . $id . '"';

Now do a var_dump( $sql); to see your new SQL statement.

Answer 2

this is not a mysql problem. mysql will only see what you put into that string. eg dump out the query string BEFORE you do mysql_query. I'm guessing you're doing this query somewhere else and have run into scoping problems. And yes, this is lazy. No it's not "smart". you're just making MORE work for yourself. What's wrong with doing

INSERT ... VALUES jto_can1=$can[0], jto_can2=$can[1], etc...