Crap-ish CSV Parser

CsvMapper.php

<?php
/**
 * Map CSV columns to fields
 * 
 * somefile.csv content = "some guy, 5 Road Street, Town, Postcode"
 * 
 * $mapper = new CsvMapper('/tmp/somefile.csv');
 * $mapper->mapField('A', 'name')->filter('name', function($value){ return ucwords($value); });
 * $mapper->mapAggregateField(array('B', C', D'), 'address', ', ');
 * $mapper->mapLiteral('source', 'unknown');
 * 
 * foreach($mapper as $row):
 *     echo $row['name'], ' | ', $row['address'], ' | ', $row['source']; 
 * endforeach;
 * 
 * //Result:  Some Guy | 5 Road Street, Town, Postcode | unknown
 * 
 */
class CsvMapper implements Iterator {

    private $_file;
    private $_mapping = array();

    public function __construct($filePath)
    {
        $this->_file = new SplFileObject($filePath);
        $this->_file->setFlags(SplFileObject::READ_CSV);
    }

    //a single column mapping to a single field
    public function mapField($column, $field)
    {
        $this->_mapping[] = array('column'=>(is_numeric($column) ? $column : $this->_alphaToNum($column)), 'field'=>$field, 'delimiter'=>'');
        return $this;
    }

    //several columns that are joined together to form the field value
    public function mapAggregateField(array $columns, $field, $delimiter='::')
    {
        $numericColumns = array();
        foreach($columns as $column):
            $numericColumns[] = (is_numeric($column) ? $column : $this->_alphaToNum($column));
        endforeach;
        $this->_mapping[] = array('column'=>$numericColumns, 'field'=>$field, 'delimiter'=>$delimiter);
    }

    //a fake column that is just a literal value
    public function mapLiteralField($field, $value){
        $this->_mapping[] = array('field'=>$field, 'value'=>$value, 'column'=>null, 'delimiter'=>null);
    }


    private function _alphaToNum($alphabetChar)
    {
        $alphabet = array('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z');

        if(!$alphabetChar){
            throw new Exception('No Column Letter Given');
        }

        if(strlen($alphabetChar) == 1){
            return array_search($alphabetChar, $alphabet);
        } else {
            // e.g. AB AC AD 
            throw new Exception('> Z Not Implemented. Get a Dev to add this functionality.');
        }
    }

    public function filterField($field, Closure $callback)
    {
        foreach($this->_mapping as $key=>$mapping):
            if($mapping['field'] == $field){
                $this->_mapping[$key]['filter'] = $callback;
                return $this;
            }
        endforeach;
        return $this;
    }

    private function getMappedRow($row)
    {
        $mappedRow = array();
        foreach($this->_mapping as $mapping):

            if(isset($mapping['value']))
            {
                //literal set for this field - just set it and move on
                $fieldValString = trim($mapping['value']);
            }
            else {
                $fieldVal = array();
                if(is_array($mapping['column']))
                {
                    //aggregate field
                    foreach($mapping['column'] as $column):
                        if(!empty($row[$column]))
                        {
                            $fieldVal[] = trim($row[$column]);
                        }
                    endforeach;
                } else {
                    if(!empty($row[$mapping['column']]))
                    {
                        $fieldVal[] =  trim($row[$mapping['column']]);
                    }
                }

                //implode to string
                $fieldValString = implode($mapping['delimiter'], $fieldVal);
            }

            //apply filter where applicable
            $mappedRow[$mapping['field']] = isset($mapping['filter']) ? $mapping['filter']($fieldValString) : $fieldValString;
        endforeach;
        return $mappedRow;
    }

    public function rewind()
    {
        return $this->_file->rewind();
    }

    public function current()
    {
         return $this->getMappedRow($this->_file->current());
    }

    public function key()
    {
        return $this->_file->key();
    }

    public function next()
    {
        return $this->_file->next();
    }

    public function valid()
    {
        return $this->_file->valid();
    }

}