imagejpeg() failed to save image

Question

Using imagejpeg() in the code to save the image failed, prompting insufficient permissions

Code description:

imagejpeg($img, 'haha.jpg');

Error Description:

imagejpeg(haha.jpg): failed to open stream: Permission denied in /var/www/html/index.php on line 33, referer: http://192.168.126.135/index.php

But I have given 777 permission to the folder. I don’t understand. Please give me some advice.