Aug 6, 2015
While making modifications to the theme's PHP, CSS or others files in WordPress, the changes might not stay after it is updated. Automated updates will definitely remove all the previous files and ...
It is not at all recommended to make changes to a theme’s files in WordPress. Theme are updated at certain intervals. When the update is released, you are highly encouraged to perform the update so you get the latest features and the security vulnerabilities are patched as well.
But if you have made changes to the theme’s original files and then you update the theme, your own modifications will not stay. To keep them forever, make use of child themes.