Avvisa PDO MySQL-satsen om ett angivet värde finns i ett fält?

Om du använder PDO kan du bara fånga undantaget och kontrollera statuskoden, t.ex.

// make sure you're set to throw exceptions
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $pdo->prepare('INSERT INTO `user` (`email`) VALUES (?)');
try {
    $stmt->execute([$email]);
} catch (PDOException $e) {
    $errorInfo = $stmt->errorInfo(); // apparently PDOException#getCode() is pretty useless
    if ($errorInfo[1] == 1586) {
        // inform user, throw a different exception, etc
    } else {
        throw $e; // a different error, let this exception carry on
    }        
}

Se http://dev.mysql. com/doc/refman/5.5/en/error-messages-server.html#error_er_dup_entry_with_key_name

Processen skulle vara liknande om du använder MySQLi

$stmt = $mysqli->prepare('INSERT INTO `user` (`email`) VALUES (?)');
$stmt->bind_param('s', $email);
if (!$stmt->execute()) {
    if ($stmt->errno == 1586) {
        // inform user, throw a different exception, etc
    } else {
        throw new Exception($stmt->error, $stmt->errno);
    }
}