php - PHP 错误：mysqli_free_result($result);

Question

这个错误的解决方法是什么：

警告：mysqli_free_result() 期望参数 1 为 mysqli_result，在

$result = HSDB::getInstance()->selectlast_classification(); 
#while ($row = mysqli_fetch_array($result)); { 
while ($row_cnt = $result->num); { 
  $fkclassification = $row["pkid"]; 
} 
mysqli_free_result($result);

Answer 1

错误解释。您必须为函数提供 MySQLi 资源句柄mysqli_free_result()

Answer 2

见mysqli_free_result

result
仅限过程样式：mysqli_query()、mysqli_store_result() 或 mysqli_use_result() 返回的结果集标识符。

当mysqli_query的返回值因错误而为 false 时，可能会发生此错误。mysqli_*()您可以通过检查所有调用的返回值来避免这种情况。例如

$result = mysqli_query($mysqli, 'select * from mytable) or die(mysqli_error($mysqli));

或者

$result = mysqli_query($mysqli, 'select * from mytable);
if ($result === false) {
    // error handling
}

Answer 3

如果你有

$myConnection = mysqli_connect($db_host, $db_username, $db_pass, $db_name) 
or die ("could    not connect to mysql");  
$sql = "SELECT blabla from blalala where bla=1";
$query = mysqli_query($myConnection,$sql) or die (mysqli_error($myConnection));
while ($row=mysqli_fetch_array($query)){
  //do something 
}

比你能做的：

mysqli_free_result($query);