Example of CSV handler for PHP

CSVFile.php

<?php
declare(strict_types=1);

final class CSVFile
{
	const HEADERS_NONE = 0;
	const HEADERS_VERBATIM = 1;
	const HEADERS_NORMALIZED = 2;

	private SplFileObject $file;

	private function __construct(SplFileObject $file)
	{
		$this->file = $file;
	}

	public static function fromRequestData($data): static {
		if (empty($data)) {
			throw new BadRequestException('File upload failed, try again.');
		}
		if ($data['error'] !== 0) {
			$reason = match ($data['error']) {
				UPLOAD_ERR_INI_SIZE => 'File too large',
				UPLOAD_ERR_FORM_SIZE => 'File too large',
				UPLOAD_ERR_PARTIAL => 'File upload incomplete',
				UPLOAD_ERR_NO_FILE => 'No file uploaded',
				UPLOAD_ERR_NO_TMP_DIR => 'No temporary directory',
				UPLOAD_ERR_CANT_WRITE => 'Failed to write file to disk',
				UPLOAD_ERR_EXTENSION => 'File upload stopped by extension',
				default => 'Unknown error occurred'
			};
			throw new BadRequestException('File upload failed: '. $reason);
		}
		$allowed_mime = [
			'text/x-comma-separated-values',
			'text/comma-separated-values',
			'application/octet-stream',
			'application/vnd.ms-excel',
			'application/x-csv',
			'text/x-csv',
			'text/csv',
			'application/csv',
			'application/excel',
			'application/vnd.msexcel',
			'text/plain'
		];
		if (empty($data['type']) || !in_array($data['type'], $allowed_mime)) {
			throw new BadRequestException('Invalid file type ('.$data['type'].'), expecting CSV file.');
		}
		if (empty($data['tmp_name']) || !is_uploaded_file($data['tmp_name'])) {
			throw new BadRequestException('Session upload failed, please try again.');
		}
		if ($data['error'] !== \UPLOAD_ERR_OK) {
			throw new BadRequestException(
				"Error uploading session file (error code {$data['error']}), is file corrupted?"
			);
		}
		try {
			$file = new SplFileObject($data['tmp_name'], 'r');
		} catch (\RuntimeException $e) {
			throw new BadRequestException('Could not open file for processing: ' . $e->getMessage());
		}

		return new self($file);
	}

	public function getIterator(
		int $headersStyle = self::HEADERS_NONE,
		string $separator = ',',
		string $enclosure = '"',
		string $escape = '\\'
	): Generator {
		$this->file->setFlags(
			SplFileObject::READ_CSV |		// Parse CSV
			SplFileObject::SKIP_EMPTY |	  // Skip empty lines
			SplFileObject::READ_AHEAD |	  // Read ahead optimization
			SplFileObject::DROP_NEW_LINE	 // Drop newlines
		);

		$this->file->setCsvControl($separator, $enclosure, $escape);

		if ($headersStyle > self::HEADERS_NONE && !$this->file->eof()) {
			$headers = $this->file->fgetcsv();

			if ($headersStyle === self::HEADERS_NORMALIZED) {
				// Normalize headers by removing whitespace and converting to lowercase
				$headers = array_map(fn($header) => str_replace(' ', '_', strtolower(trim($header))), $headers);
			}

		}

		while (!$this->file->eof()) {
			$row = $this->file->fgetcsv();

			// Skip invalid or empty rows
			if ($row === false) {
				continue;
			}
			// Skip rows that are empty or contain only empty values
			if (empty($row) || (count($row) === 1 && empty(trim($row[0])))) {
				continue;
			}

			// If using headers, map the row values to the headers
			if ($headersStyle > self::HEADERS_NONE) {
				$row = array_combine($headers, $row);
				if ($row === false) {
					throw new RuntimeException('Invalid CSV format: inconsistent number of columns');
				}
			}

			yield $row;
		}
	}

}