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Defining the offsetUnset() method - PHP

In this fifth part of a six-part series on the Iterator, Countable and ArrayAccess SPL interfaces, I implement the rest of the methods declared by the ArrayAccess SPL interface within the “MySQLi_ResultWrapper” class that you saw in a previous part. Once this process is completed, the class will be able to treat records in database result sets as if they were plain array elements.

TABLE OF CONTENTS:
  1. Implementing More Methods of the ArrayAccess SPL Interface
  2. Review: the MySQLiWrapper and MySQLi_ResultWrapper classes
  3. Defining the offsetUnset() method
  4. Finish defining the methods of the ArrayAccess interface
By: Alejandro Gervasio
Rating: starstarstarstarstar / 1
April 12, 2010

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Due to the fact that the sample “MySQLi_ResultWrapper” class at this point  defines only two methods of the four declared by the ArrayAccess interface, we must add to the class another of these required methods. In this case, the method will be “offsetUnset(),” which won’t be specifically implemented.

After including this brand new method, the source code of the class will be as follows:

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);

    }

       

    // 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();

    }

}

As you can see, adding to the above “MySQLi_ResultWrapper” class the “offsetUnset()” method doesn’t change its behavior, since this method has no  concrete implementation, but of course you may want to change this on your own to fit your personal needs.

However, we’re still not done with this class. The ArrayAccess interface requires any implementer of it to include another method called “offsetGet().” Thus, in the section to come I’m going to add this last method to the class, which as you’ll see will be concretely implemented.   

To see how the “MySQLi_ResultWrapper” class will look after implementing this final interface method, click on the link below and read the next few lines.



 
 
>>> More PHP Articles          >>> More By Alejandro Gervasio
 

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