PDO更新查询绝对没有任何意义

Question

So yesterday I ran into this error which I can't seem to get a hang of. The piece of code below is supposed to make two posts in a recursive MariaDB table switch places.

$cid is the ID of the post that is supposed to switch place, up or down. $pid is the parent ID. $ord is which place the post has under the parent. $dir is in which direction the post is supposed to be moved, up or down.

Then the post in the position that the first post is supposed to move to is taking the first posts initial place.

<?php

    $cid = isset($_GET['cid']) ? $_GET['cid'] : "";
    $pid = isset($_GET['pid']) ? $_GET['pid'] : "";
    $ord = isset($_GET['ord']) ? $_GET['ord'] : "";
    $dir = isset($_GET['dir']) ? $_GET['dir'] : "";

    if($cid == "" || $pid == "" || $ord == "" || $dir == "") die('nu gick det åt pipsvängen...');

    if($dir == "up") {
        $opos = $ord--;
    } elseif($dir == "down") {
        $opos = $ord++;
    } else {
        die('ingen riktning');
    };

    $ostmt = $dbh -> prepare("UPDATE csa_categories SET ordning = :onp WHERE foralder = :pid AND ordning = :oop");
    $ostmt -> bindValue(":onp", $ord);
    $ostmt -> bindValue(":pid", $pid);
    $ostmt -> bindValue(":oop", $opos);

    $ostmt -> execute();

    $cstmt = $dbh -> prepare("UPDATE csa_categories SET ordning = :cnp WHERE id = :cid");
    $cstmt -> bindValue(":cnp", $opos);
    $cstmt -> bindValue(":cid", $cid);

    $cstmt -> execute();

?>

This does absolutely nothing. I doesn't change anything in the table and there are no errors whatsoever.

Answer 1

So today I finally made it! I was looking at the whole thing wrong. There where no flaws in the script, except for maybe the fact that I didn't comment it. Today I started commenting everything and gave my variables better names and it turns out, I've been thinking wrong. The update queries worked, but they updated the wrong lines, hence it seemed like nothing happened.

Here is the final solution:

<?php

    $absid = isset($_GET['cid']) ? $_GET['cid'] : "";   // ID of absolute row
    $parid = isset($_GET['pid']) ? $_GET['pid'] : "";   // Absolute row's parent ID
    $abspos = isset($_GET['ord']) ? $_GET['ord'] : "";  // Current position of absolute row
    $newrelpos = $abspos;                               // New position of relative row
    $dir = isset($_GET['dir']) ? $_GET['dir'] : "";     // Direction to move absolute row

    if($absid == "" || $parid == "" || $abspos == "" || $dir == "") die('missing variable(s)');

    // Generate absolute row's new position
    if($dir == "up") {
        $newabspos = $abspos - 1;
    } elseif($dir == "down") {
        $newabspos = $abspos + 1;
    } else {
        die('direction not set');
    };

    $relpos = $newabspos;   // Current position of relative row

    // Fetch relative row's ID
    $stmt = $dbh -> prepare("SELECT id FROM csa_categories WHERE foralder = :parid AND ordning = :pos");
    $stmt -> bindValue(":parid", $parid);
    $stmt -> bindValue(":pos", $relpos);
    $stmt -> execute();
    $row = $stmt -> fetch();

    $relid = $row['id'];    // Relative row's ID

    // Update absolute row
    $astmt = $dbh -> prepare("UPDATE csa_categories SET ordning = :newabspos WHERE id = :absid");
    $astmt -> bindValue(":newabspos", $newabspos);
    $astmt -> bindValue(":absid", $absid);
    $astmt -> execute();

    // Update relative row
    $rstmt = $dbh -> prepare("UPDATE csa_categories SET ordning = :newrelpos WHERE id = :relid");
    $rstmt -> bindValue(":newrelpos", $newrelpos);
    $rstmt -> bindValue(":relid", $relid);
    $rstmt -> execute();

?>