Simple class to iterate a CSV file quickly, allowing the user to manipulate the value of each field

Reader.php

<?php

class Reader
{
    protected $fields = [];
    protected $filters = [];

    public function read($file)
    {
        try {
            $handle = fopen($file, 'r');

            while ($line = fgetcsv($handle)) {
                foreach ($this->filters as $check) {
                    if (false === call_user_func($check, $line)) {
                        continue 2;
                    }
                }

                yield $line;
            }
        } finally {
            fclose($handle);
        }
    }

    public function fields(array $fields)
    {
        foreach ($fields as $header => $callback) {
            $this->field($header, $callback);
        }

        return $this;
    }

    public function field($header, $callback, $position = 0)
    {
        if (!$position) {
            $position = count($this->fields) + 10;
        }

        $this->fields[] = [
            'header' => $header,
            'position' => $position,
            'callback' => $callback
        ];

        return $this;
    }

    public function sort($on = 'position', $order = SORT_ASC)
    {
        usort($this->fields, function($a, $b) use ($on, $order) {
            if ($a[$on] == $b[$on])
                return 0;
            else
                return ($order===SORT_ASC ? $a[$on] > $b[$on] : $a[$on] < $b[$on]) ? 1 : -1;
        });
    }

    public function filter(Closure $callback)
    {
        $this->filters[] = $callback;

        return $this;
    }

    public function row(array $row)
    {
        $fields = [];
        foreach ($this->fields as $field) {
            if ($field['callback'] instanceof Closure) {
                $fields[] = call_user_func($field['callback'], $row);
            } else {
                $fields[] = $row[$field['callback']];
            }
        }

        return $fields;
    }

    public function headers()
    {
        return array_map(function($field) {
            return $field['header'];
        }, $this->fields);
    }
}

usage.php

<?php

$reader = new Reader();

$reader->fields(array(
    'Call ID' => 0,
    'Call Type' => function($call) {
        return $call[8] === 'O' ? 'Outbound' : 'Inbound';
    },
    'NGN' => 1,
    'Date' => 2,
    'Duration' => function($call) {
        return round($call[4] / 60, 3);
    },
    'Type' => 5,
    'Cost' => function($call) {
        return round($call[6], 3);
    },
    'Caller' => 7,
    'Target' => function($call) {
        return 'N/A';
    }
));

$reader->filter(function($call) {
    if (in_array($call[0], array('HEADER', 'TRAILER'))) {
        return false;
    }

    return true;
});

$headers = $reader->headers();
$rows = $reader->read('/path/to/file.csv');