A CSV Parser in PHP

CsvParser.php

<?php

class CsvParser
{
    private $delimiter;
    private $fileHandle;
    private $buffer;
    private $bufferSize;
    private $header;

    public function __construct($filePath, $delimiter = ',', $hasHeader = true, $bufferSize = 8192)
    {
        $this->delimiter = $delimiter;
        $this->bufferSize = $bufferSize;
        $this->buffer = '';
        $this->header = null;

        if (!file_exists($filePath)) {
            throw new Exception("File not found: {$filePath}");
        }

        $this->fileHandle = fopen($filePath, 'r');
        if ($this->fileHandle === false) {
            throw new Exception("Unable to open file: {$filePath}");
        }

        if ($hasHeader) {
            $this->header = $this->readRow();
            if ($this->header === false) {
                $this->header = null;
            }
        }
    }

    public static function fromFile($filePath, $delimiter = ',', $hasHeader = true, $bufferSize = 8192)
    {
        return new self($filePath, $delimiter, $hasHeader, $bufferSize);
    }

    public static function fromResource($resource, $delimiter = ',', $hasHeader = true, $bufferSize = 8192)
    {
        if (!is_resource($resource)) {
            throw new Exception("Invalid resource provided");
        }

        $reflection = new ReflectionClass(__CLASS__);
        $parser = $reflection->newInstanceWithoutConstructor();

        $parser->delimiter = $delimiter;
        $parser->bufferSize = $bufferSize;
        $parser->buffer = '';
        $parser->header = null;
        $parser->fileHandle = $resource;

        if ($hasHeader) {
            $parser->header = $parser->readRow();
            if ($parser->header === false) {
                $parser->header = null;
            }
        }

        return $parser;
    }

    public function parse()
    {
        while (($row = $this->readRow()) !== false) {
            yield $row;
        }
    }

    public function getHeader()
    {
        return $this->header;
    }

    private function readRow()
    {
        $row = [];
        $field = '';
        $inQuotes = false;
        $quoteChar = null;
        $fieldStarted = false;

        while (true) {
            if (strlen($this->buffer) < $this->bufferSize) {
                $chunk = fread($this->fileHandle, $this->bufferSize);
                if ($chunk === false || $chunk === '') {
                    if (feof($this->fileHandle)) {
                        if ($fieldStarted || strlen($field) > 0 || count($row) > 0) {
                            $row[] = $field;
                            return $row;
                        }
                        return false;
                    }
                    break;
                }
                $this->buffer .= $chunk;
            }

            if (strlen($this->buffer) === 0) {
                if ($fieldStarted || strlen($field) > 0 || count($row) > 0) {
                    $row[] = $field;
                    return $row;
                }
                return false;
            }

            $i = 0;
            $bufferLen = strlen($this->buffer);

            while ($i < $bufferLen) {
                $char = $this->buffer[$i];
                $nextChar = ($i + 1 < $bufferLen) ? $this->buffer[$i + 1] : null;

                if (!$inQuotes) {
                    if ($char === '"' || $char === "'") {
                        $inQuotes = true;
                        $quoteChar = $char;
                        $fieldStarted = true;
                        $i++;
                        continue;
                    } elseif ($char === $this->delimiter) {
                        $row[] = $field;
                        $field = '';
                        $fieldStarted = false;
                        $i++;
                        continue;
                    } elseif ($char === "\n" || ($char === "\r" && $nextChar !== "\n")) {
                        if ($char === "\r" && $nextChar === "\n") {
                            $i += 2;
                        } else {
                            $i++;
                        }
                        $row[] = $field;
                        $this->buffer = substr($this->buffer, $i);
                        return $row;
                    } else {
                        $field .= $char;
                        $fieldStarted = true;
                        $i++;
                        continue;
                    }
                } else {
                    if ($char === $quoteChar) {
                        if ($nextChar === $quoteChar) {
                            $field .= $quoteChar;
                            $i += 2;
                            continue;
                        } else {
                            $inQuotes = false;
                            $quoteChar = null;
                            $i++;
                            continue;
                        }
                    } elseif ($char === "\n" || $char === "\r") {
                        if ($char === "\r" && $nextChar === "\n") {
                            $field .= "\r\n";
                            $i += 2;
                        } else {
                            $field .= $char;
                            $i++;
                        }
                        continue;
                    } else {
                        $field .= $char;
                        $i++;
                        continue;
                    }
                }
            }

            $this->buffer = '';
        }

        if ($fieldStarted || strlen($field) > 0 || count($row) > 0) {
            $row[] = $field;
            return $row;
        }

        return false;
    }

    public function close()
    {
        if ($this->fileHandle && is_resource($this->fileHandle)) {
            fclose($this->fileHandle);
            $this->fileHandle = null;
        }
        $this->buffer = '';
        $this->header = null;
    }

    public function __destruct()
    {
        $this->close();
    }
}