php更新sql和查询

Question

I want to do a query in php, output the data on the page and then modify it in the database.

How do I do that?

Currently I do it like this but it dose not work:

$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT * FROM pics WHERE id = '$id'";
$result = $conn->query($sql);
    // output data of each row
    while($row = $result->fetch_assoc()) {
       $dir = $row["dir"];
       $likes = $row["likes"];
    }

$sqlq = "UPDATE pics SET likes='$likes+1' WHERE id='$id'";

$conn->query($sqlq);

$conn->close();

But the like dose not add to the database.

Answer 1

If you echo your $sqlq out using

echo $sqlq;

you'll see that the '$likes+1' isn't doing what you expect.

You could really simplify it by doing

$sqlq = "UPDATE pics SET likes=likes+1 WHERE id='$id'";

which removes any risk of two users updating the database at teh same time overwriting each other.

But you should really check out using "parameterized queries" as that would solve all your problems (and may your queries safer). Check the examples in the manual http://php.net/manual/en/mysqli-stmt.bind-param.php