Question

While writing a login system for a web project Im working on I came across the problem of binding an unknown number of parameters and found this function on the php manual pages. I always like to fully understand an peice of code I put into anything Im working on and Im quite stumped as to how a few sections of this function work.

Ive commented everything I think i understand(if im wrong please let me know) and left my major questions in the comments:

<?php
    function getresult($stmt) {

        //Define var for holding the result
        $result = array();

        //asign metadata of the statments result
        $metadata = $stmt->result_metadata();

        //grab the feilds from the metadata and assign to var
        $fields = $metadata->fetch_fields();

        //for loop with internal break
        for (;;) {

            //pointers array (not sure why this is an array and not a stdClass)
            $pointers = array();

            //row empty class
            $row = new stdClass();


            //set pointers array to the value of the passed statement (casting $pointers to mysqli_stmt class I assume(?)   
            $pointers[] = $stmt;

            //iterate through all fields
            foreach ($fields as $field) {
                //each time set $fieldname to the name from the current element of $fields
                $fieldname = $field->name;

                //?? this is my big issue no idea whats going on here $row hasnt been set from what i can see, and no idea why its being refered to by reference and not value
                $pointers[] = &$row->$fieldname;
            }

            //call bind result for all values
            call_user_func_array(mysqli_stmt_bind_result, $pointers);

            //internal break if 
            if (!$stmt->fetch()) {

                //if there is nothing left to fetch break
                break;
            }

            //set the result
            $result[] = $row;
        }

        //free resources
        $metadata->free();

        //return result
        return $result;
    }
?>

Thanks in advance!

Answer 1

It creates a new stdClass (pretty much like an empty array) for each row.

With $pointers[] = &$row->$fieldname; a reference to the various fields of the object is stored.

After that, mysqli_stmt_bind_result is used to tell mysqli where to store the data of the next row. When calling $stmt->fetch(), mysqli assigns it to the references in $pointers and thus to the fields in the $row object.

$pointers is an array because mysqli_stmt_bind_result expects one. Objects do not have 0..n fields but rather named values – so to assign columns based on their position using a non-associative array makes much more sense.

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It does pretty much the same what mysqli::fetch_object() does.