Why must ob_clean(); be added to the PHP image verification code to display normally.

ob_clean这个函数的作用就是用来丢弃输出缓冲区中的内容，如果你的网站有许多生成的图片类文件，那么想要访问正确，就要经常清除缓冲区。

If you work on an extremely large project with a lot of source and required files, like myself, you will be well-advised to always clear the output buffer prior to creating an image in php.