yii\validators\FileValidator::validateMimeType PHP Method

    protected function validateMimeType($file)
    {
        $fileMimeType = FileHelper::getMimeType($file->tempName);
        foreach ($this->mimeTypes as $mimeType) {
            if ($mimeType === $fileMimeType) {
                return true;
            }
            if (strpos($mimeType, '*') !== false && preg_match($this->buildMimeTypeRegexp($mimeType), $fileMimeType)) {
                return true;
            }
        }
        return false;
    }