friendica-addons/js_upload/file-uploader/server/php.php

<?php

/**
 * Handle file uploads via XMLHttpRequest
 */
class qqUploadedFileXhr {
	/**
	 * Save the file to the specified path
	 * @return boolean TRUE on success
	 */
	public function save(string $path): bool
	{
		$input = fopen('php://input', 'r');
		$temp = tmpfile();
		$realSize = stream_copy_to_stream($input, $temp);
		fclose($input);

		if ($realSize != $this->getSize()) {
			return false;
		}

		$target = fopen($path, 'w');
		fseek($temp, 0, SEEK_SET);
		stream_copy_to_stream($temp, $target);
		fclose($target);

		return true;
	}

	public function getName(): string
	{
		return $_GET['qqfile'];
	}

	public function getSize(): int
	{
		if (isset($_SERVER['CONTENT_LENGTH'])) {
			return (int)$_SERVER['CONTENT_LENGTH'];
		} else {
			throw new Exception('Getting content length is not supported.');
		}
	}
}

/**
 * Handle file uploads via regular form post (uses the $_FILES array)
 */
class qqUploadedFileForm {
	/**
	 * Save the file to the specified path
	 * @return boolean TRUE on success
	 */
	public function save(string $path): bool
	{
		if(!move_uploaded_file($_FILES['qqfile']['tmp_name'], $path)) {
			return false;
		}
		return true;
	}

	public function getName(): string
	{
		return $_FILES['qqfile']['name'];
	}

	public function getSize(): int
	{
		return $_FILES['qqfile']['size'];
	}
}

class qqFileUploader {
	private $allowedExtensions = [];
	private $sizeLimit = 10485760;
	private $file;

	public function __construct(array $allowedExtensions = [], $sizeLimit = 10485760)
	{
		$allowedExtensions = array_map('strtolower', $allowedExtensions);

		$this->allowedExtensions = $allowedExtensions;
		$this->sizeLimit = $sizeLimit;

		$this->checkServerSettings();

		if (isset($_GET['qqfile'])) {
			$this->file = new qqUploadedFileXhr();
		} elseif (isset($_FILES['qqfile'])) {
			$this->file = new qqUploadedFileForm();
		} else {
			$this->file = false;
		}
	}

	private function checkServerSettings()
	{
		$postSize = $this->toBytes(ini_get('post_max_size'));
		$uploadSize = $this->toBytes(ini_get('upload_max_filesize'));

		if ($postSize < $this->sizeLimit || $uploadSize < $this->sizeLimit) {
			$size = max(1, $this->sizeLimit / 1024 / 1024) . 'M';
			die("{'error':'increase post_max_size and upload_max_filesize to $size'}");
		}
	}

	private function toBytes(string $str): int
	{
		$val = (int) trim($str);
		$last = strtolower($str[strlen($str) - 1]);

		switch($last) {
			case 'g': $val *= 1024;
			case 'm': $val *= 1024;
			case 'k': $val *= 1024;
		}

		return $val;
	}

	/**
	 * Returns array('success'=>true) or array('error'=>'error message')
	 */
	public function handleUpload(string $uploadDirectory, bool $replaceOldFile = false): array
	{
		if (!is_writable($uploadDirectory)) {
			return ['error' => "Server error. Upload directory isn't writable."];
		}

		if (!$this->file) {
			return ['error' => 'No files were uploaded.'];
		}

		$size = $this->file->getSize();

		if ($size == 0) {
			return ['error' => 'File is empty'];
		}

		if ($size > $this->sizeLimit) {
			return ['error' => 'File is too large'];
		}

		$pathinfo = pathinfo($this->file->getName());
		$filename = $pathinfo['filename'];
		//$filename = md5(uniqid());
		$ext = $pathinfo['extension'];

		if($this->allowedExtensions && !in_array(strtolower($ext), $this->allowedExtensions)) {
			$these = implode(', ', $this->allowedExtensions);
			return ['error' => 'File has an invalid extension, it should be one of '. $these . '.'];
		}

		if(!$replaceOldFile) {
			/// don't overwrite previous files that were uploaded
			while (file_exists($uploadDirectory . $filename . '.' . $ext)) {
				$filename .= rand(10, 99);
			}
		}

		if ($this->file->save($uploadDirectory . $filename . '.' . $ext)) {
			return ['success' => true];
		} else {
			return ['error'=> 'Could not save uploaded file. The upload was cancelled, or server error encountered'];
		}
	}
}

// list of valid extensions, ex. array("jpeg", "xml", "bmp")
$allowedExtensions = [];

// max file size in bytes
$sizeLimit = 10 * 1024 * 1024;

$uploader = new qqFileUploader($allowedExtensions, $sizeLimit);
$result = $uploader->handleUpload('uploads/');
// to pass data through iframe you will need to encode all html tags
echo htmlspecialchars(json_encode($result), ENT_NOQUOTES);