Finish defining the methods of the ArrayAccess interface - PHP

As I stated in the section that you just read, it’s mandatory to provide the “MySQLi_ResultWrapper” class with an “offsetGet()” method to confirm the contract required by the ArrayAccess interface. In consonance with this, below I listed the finished version of the class, this time including the method in question.

Look at the following code sample:

class MySQLi_ResultWrapper extends MySQLi_Result implements Iterator, ArrayAccess, Countable

{

    private $_pointer = 0;

   // fetch row as an object

    public function fetchObject()

    {

        if (!$row = $this->fetch_object())

        {

            return NULL;

        }

        return $row;

    }

    // fetch row as an associative array

    public function fetchAssocArray()

    {

        if (!$row = $this->fetch_assoc())

        {

            return NULL;

        }

        return $row;

    }

    // fetch row as an enumerated array

    public function fetchNumArray()

    {

        if (!$row = $this->fetch_row())

        {

            return NULL;

        }

        return $row;

    }

    // fetch all rows

    public function fetchAll($type = MYSQLI_ASSOC)

    {

        if ($type !== MYSQLI_ASSOC AND $type !== MYSQLI_NUM AND $type !== MYSQLI_BOTH)

        {

            $type = MYSQLI_ASSOC;

        }

        if (!$rows = $this->fetch_all($type))

        {

            return NULL;

        }

        return $rows;  

    }

    // get definition information on fields

    public function fetchFieldsInfo()

    {

        if (!$fieldsInfo = $this->fetch_fields())

        {

            throw new Exception('No information available for table fields.');

        }

        return $fieldsInfo;

    }

    // get definition information on next field

    public function fetchFieldInfo()

    {

        if (!$fieldInfo = $this->fetch_field())

        {

            throw new Exception('No information available for current table field.');   

        }

        return $fieldInfo;

    }

    // move pointer in result set to specified offset

    public function movePointer($offset)

    {

        $offset = abs((int)$offset);

        $limit = $this->num_rows - 1;

        if ($limit <= 0 OR $offset > $limit)

        {

            return NULL;

        }

        unset($limit);

        return $this->data_seek($offset);

    }

    // count rows in result set (implementation required by 'count()' method in Countable interface)

    public function count()

    {

        return $this->num_rows;

    }

    // reset result set pointer (implementation required by 'rewind()' method in Iterator interface)

    public function rewind()

    {

        $this->_pointer = 0;

        $this->movePointer($this->_pointer);

        return $this; 

    }

    // get current row set in result set (implementation required by 'current()' method in Iterator interface)

    public function current()

    {

        if (!$this->valid())

        {

            throw new Exception('Unable to retrieve current row.');

        }

        $this->movePointer($this->_pointer);

        return $this->fetchObject();

    }

    // get current result set pointer (implementation required by 'key()' method in Iterator interface)

    public function key()

    {

        return $this->_pointer;

    }

    // move forward result set pointer (implementation required by 'next()' method in Iterator interface)

    public function next()

    {

        ++$this->_pointer;

        $this->movePointer($this->_pointer);

        return $this;

    }

    // determine if result set pointer is valid or not (implementation required by 'valid()' method in Iterator interface)

    public function valid()

    {

        return $this->_pointer < $this->num_rows;

    }

    // determine if the given offset exists (implementation required by 'offsetExists()' method in ArrayAccess interface)

    public function offsetExists($offset)

    {

        $this->movePointer($offset);

        $row = $this->fetchObject();

        return isset($row);

    }

    // get row according to given offset (implementation required by 'offsetExists()' method in ArrayAccess interface)

    public function offsetGet($offset)

    {

        $this->_pointer = abs((int)$offset);

        return $this->current();

    }

    // not implemented (required by 'offsetSet()' method in ArrayAccess interface)

    public function offsetSet($offset, $value){}

        // not implemented (required by 'offsetUnset()' method in ArrayAccess interface)

    public function offsetUnset($offset){}

    // free up result set

    public function __destruct()

    {

        $this->close();

    }

}

Mission accomplished. At this stage, the “MySQLi_ResultWrapper” class implements the required “offsetGet()” method, which gives it the ability to access a record within a result set by specifying only an offset. With this last addition, the class is finally ready to be properly tested, without having to get (at least in theory) an ugly complaint from the PHP engine.

However, the full details of this testing process will be covered in the following tutorial.

Final thoughts

In this fifth episode of the series, I finished implementing the rest of the methods declared by the ArrayAccess SPL interface within the “MySQLi_ResultWrapper” class that you saw previously. With this process completed, the class can treat records in database result sets as if they were plain array elements.

Now that this sample class is ready to be tested, in the last article I’m going to code a few illustrative examples that will put the class in action, so you can see its actual functionality.

Don’t miss the final chapter of the series!