How to read data from database change them and update database

Question

I need to read data from database then edit these data with php and update database with these data.

I can get data from database but not able to write them back (I add another query to see if value is changed)

I’ve tried to use phpMyAdmin to see if values are changed but they are stil same

$POWER = "";
if ($pressed == "1") {
    echo "pressed\n";
    $sql = "SELECT `POWER` FROM `VolleyTest` WHERE ID = 1";
    $result = mysqli_query($conn, $sql);
    while ($row = mysqli_fetch_row($result)) {
        $POWER = $row[0];
        echo "pressed power request $row[0]\n";
    }
    if ($POWER == "ON") {
        $sql = 'UPDATE `VolleyTest` SET `POWER`=\"OFF\" WHERE ID = 1';
        $conn->query($sql);
        echo " POWER ON to OFF\n";
    } else if ($POWER == "OFF") {
        $sql = 'UPDATE `VolleyTest` SET `POWER`=\"ON\" WHERE ID = 1';
        $conn->query($sql);
        echo " POWER OFF to ON\n";
    }
}
$sql = "SELECT `POWER` FROM `VolleyTest` WHERE ID = 1";
$result = mysqli_query($conn, $sql);
while ($row = mysqli_fetch_row($result)) {
    $POWER = $row[0];
    echo "$row[0]\n";
}
echo $POWER; //. "  ". $pressed . "  " . $_POST['key'];

Answer 1

You dont need to escape double quotes inside a single quoted string.

Doing that generates a string like this

UPDATE `VolleyTest` SET `POWER`=\"ON\" WHERE ID = 1

So this may work

$POWER = "";
if ($pressed == "1") {
    echo "pressed\n";
    $sql = "SELECT `POWER` FROM `VolleyTest` WHERE ID = 1";
    $result = mysqli_query($conn, $sql);
    while ($row = mysqli_fetch_row($result)) {
        $POWER = $row[0];
        echo "pressed power request $row[0]\n";
    }
    if ($POWER == "ON") {
        $sql = 'UPDATE `VolleyTest` SET `POWER`="OFF" WHERE ID = 1';
        $conn->query($sql);
        echo " POWER ON to OFF\n";
    } else if ($POWER == "OFF") {
        $sql = 'UPDATE `VolleyTest` SET `POWER`="ON" WHERE ID = 1';
        $conn->query($sql);
        echo " POWER OFF to ON\n";
    }
}
$sql = "SELECT `POWER` FROM `VolleyTest` WHERE ID = 1";
$result = mysqli_query($conn, $sql);
while ($row = mysqli_fetch_row($result)) {
    $POWER = $row[0];
    echo "$row[0]\n";
}
echo $POWER; //. "  ". $pressed . "  " . $_POST['key'];