Cannot use call_user_func_array on mysqli_stmt obj

问题:

I am writing a wrapper class for MySQLi. In there, I am writing a function to accept a query and variable number of parameters where I can invoke mysqli_stmt::bind_param. Here is the code:

<?php
    class DbHelper {
        ....
        public function Execute($query, $params){
            $this->open(); # Opens a connection to the database using MySQLi API
            $stmt = $this->mysqli->prepare($query);
            try{
                $result = call_user_func_array(array($stmt, 'bind_param'), $params);
            }
            catch(Exception $ex){
                # Handle Exception
            }
        }
        ....
    }
?>

Here's how I am calling the function:

<?php
    $db = new DbHelper();
    $params = array('i', $stateID);
    $result = $db->Execute('SELECT * FROM mst_cities WHERE State_ID = ?', $params);    
?>

When I run the code, I get an warning as this:
Warning: Parameter 2 to mysqli_stmt::bind_param() expected to be a reference, value given in......

What should I do?

回答1:

From the docs:

Note:

Care must be taken when using mysqli_stmt_bind_param() in conjunction with call_user_func_array(). Note that mysqli_stmt_bind_param() requires parameters to be passed by reference, whereas call_user_func_array() can accept as a parameter a list of variables that can represent references or values.

There are some workarounds in the comments, for example see this:

call_user_func_array(array($stmt, 'bind_param'), refValues($params));

function refValues($arr)
{
    if (strnatcmp(phpversion(),'5.3') >= 0) //Reference is required for PHP 5.3+
    {
        $refs = array();
        foreach($arr as $key => $value)
            $refs[$key] = &$arr[$key];
        return $refs;
    }
    return $arr;
}