PDO Update语句，在PHPmyadmin中工作，但在PHP中不工作[关闭]

I am trying to make an update statement with PDO and i found out it doesn´t work.

I have testet the SQL statement in phpMyadmin and it works if i put '' arround the passkey, but why wont it work with this ?

INFO: The passkey is a md5 string

 <?php

include('../mysql/pdoconn.php');

$passkey = $_GET['passkey'];

$stmt = $conn->prepare("UPDATE user SET com_code='' WHERE com_code = :passkey");
$stmt->bindParam(':passkey', $passkey , PDO::PARAM_STR);
$stmt->execute;
$error = "Jon Snow";

$stmt1 = $conn->prepare("SELECT com_code from user where com_code =''");
$stmt1->execute;
$result = $stmt1->fetchColumn();


if($result === "")
{
     $error = 'Your account is now active. You may now <a href="../signin/sign.php">Log in</a>';
    $conn = null;
} else
{
    $error = $passkey;
    $conn = null;
}
?>

i have tested that it gets the passkey, and it does, but it dont update the table...

I have tried anything, but i cant get it to work

$stmt = $conn->prepare("UPDATE user SET com_code='' WHERE com_code = :passkey");
$stmt->bindParam(':passkey', $passkey , PDO::PARAM_STR);
$stmt->execute();

1. execute() is a function
2. You don't need to quote bound parameters