相关疑难解决方法(0)

我试图从MySQL表中选择数据,但我收到以下错误消息之一:

mysql_fetch_array()期望参数1是资源,给定布尔值

要么

mysqli_fetch_array()期望参数1为mysqli_result,给定布尔值

要么

在布尔/非对象上调用成员函数fetch_array()

这是我的代码:

$username = $_POST['username'];
$password = $_POST['password'];

$result = mysql_query('SELECT * FROM Users WHERE UserName LIKE $username');

while($row = mysql_fetch_array($result)) {
    echo $row['FirstName'];
}

这同样适用于代码

$result = mysqli_query($mysqli, 'SELECT ...');
// mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given
while( $row=mysqli_fetch_array($result) ) {
    ...

和

$result = $mysqli->query($mysqli, 'SELECT ...');
// Call to a member function fetch_assoc() on a non-object
while( $row=$result->fetch_assoc($result) ) {
    ...

和

$result = $pdo->query('SELECT ...', PDO::FETCH_ASSOC);
// Invalid …