有一些我不太明白的是,在
mysqli中准备和查询.
这一个是使用MysqLi :: query来处理查询,并且已经知道缺乏安全性:
public function fetch_assoc($query)
{
$result = parent::query($query);
//$result = self::preparedStatement($query);
if($result)
{
return $result->fetch_assoc();
}
else
{
# call the get_error function
return self::get_error();
# or:
# return $this->get_error();
}
}
这是一个具有prepare-bind-execute的,具有更好的安全性,我假设,
public function fetch_assoc_stmt($sql,$types = null,$params = null)
{
# create a prepared statement
$stmt = parent::prepare($sql);
# bind parameters for markers
# but this is not dynamic enough...
//$stmt->bind_param("s",$parameter);
if($types&&$params)
{
$bind_names[] = $types;
for ($i=0; $i<count($params);$i++)
{
$bind_name = 'bind' . $i;
$$bind_name = $params[$i];
$bind_names[] = &$$bind_name;
}
$return = call_user_func_array(array($stmt,'bind_param'),$bind_names);
}
# execute query
$stmt->execute();
# these lines of code below return one dimentional array,similar to MysqLi::fetch_assoc()
$Meta = $stmt->result_Metadata();
while ($field = $Meta->fetch_field()) {
$var = $field->name;
$$var = null;
$parameters[$field->name] = &$$var;
}
call_user_func_array(array($stmt,'bind_result'),$parameters);
while($stmt->fetch())
{
return $parameters;
}
# close statement
$stmt->close();
}
但是,这两种方法都返回相同的结果,
$MysqLi = new database(DB_HOST,DB_USER,DB_PASS,DB_NAME); $sql = " SELECT * FROM root_contacts_cfm ORDER BY cnt_id DESC "; print_r($MysqLi->fetch_assoc_stmt($sql)); print_r($MysqLi->fetch_assoc($sql));
他们打印这个:
Array
(
[cnt_id] => 2
[cnt_email1] => lau@xx.net
[cnt_email2] =>
[cnt_fullname] => Lau T
[cnt_firstname] => Thiam
[cnt_lastname] => Lau
[cnt_organisation] =>
[cnt_website] =>
[cnt_biography] =>
[cnt_gender] =>
[cnt_birthday] =>
[cnt_address] =>
[cnt_postcode] =>
[cnt_telephone] =>
[cnt_note] =>
[cnt_key] =>
[cat_id] =>
[tcc_id] =>
[cnt_suspended] => 0
[cnt_created] => 2011-02-04 00:00:00
[cnt_updated] => 2011-02-04 13:54:36
)
Array
(
[cnt_id] => 2
[cnt_email1] => lau@xx.net
[cnt_email2] =>
[cnt_fullname] => Lau T
[cnt_firstname] => Thiam
[cnt_lastname] => Lau
[cnt_organisation] =>
[cnt_website] =>
[cnt_biography] =>
[cnt_gender] =>
[cnt_birthday] =>
[cnt_address] =>
[cnt_postcode] =>
[cnt_telephone] =>
[cnt_note] =>
[cnt_key] =>
[cat_id] =>
[tcc_id] =>
[cnt_suspended] => 0
[cnt_created] => 2011-02-04 00:00:00
[cnt_updated] => 2011-02-04 13:54:36
)
你应该注意到,在fetch_assoc_stmt的方法里面,我根本不用fetch_assoc.可能没有机会使用它作为准备使用不同的方式来返回结果.
所以,我的问题是使用prepare比查询更好,为什么要fetch_assoc存在?我们不应该只是忘记它,或者不应该PHP.net已经弃用? fetch_all是一样的 – 为什么我们应该把它放在第一位?
谢谢.
使用参数动态生成查询时,准备语句比纯SQL查询更为可取.在您的示例中,您的sql不包含变量,因此使用纯查询或准备语句在功能上相当.
当您必须更改参数的值时,例如,在WHERE子句中,则准备好的语句将为您增加安全性:
... WHERE col1 = ? AND col2 = ?
但是当您的查询简单而且修复时,可能需要较少的代码才能使用$MysqLi-> query($sql)以及fetch_assoc().使用直接查询而不是准备好的语句不是一个普遍的坏习惯,因为有些人可能相信.当您的查询需要参数化时,或者当必须重复编译和执行相同的查询时,您将从准备好的语句中受益.