How to solve PHP write file permission failure file_put_contents: failed to open stream: Permission denied

Problem

The file_put_contents method is used in the log writing method. Today, when executing the callback method to write the log, it prompts that there is no write permission to the file and an error message

file_put_contents: failed to open stream: Permission denied（PHP video tutorial）

Solution process

Check the log folder permissions because it is It is generated on a daily basis. There is a scheduled task that is executed regularly. The execution user is root, so the user and user group for generating the folder are both root. The execution user in the callback method is www. Write to the log method

 if(!is_dir($dir)){
        mkdir($dir,0777,true);
    }

If the directory does not exist, create the directory, but set 777 permissions when creating the folder in PHP's mkdir function. In fact, the file created still has 755 permissions. In the Linux system, there is a default permission when creating files/folders. This permission is affected by the umask setting. In the /etc/bashrc configuration file, we can find the following configuration:

if [ $UID -gt 99 ] && [ "`id -gn`" = "`id -un`" ]; then
        umask 002else
        umask 022fi

Default umask in the Linux system It is 022. After operating with our 777 &, it becomes 755. This is the reason. The settings here directly affect the default permission settings of the Linux system, not just a PHP problem. Therefore, it is not recommended to modify it directly to change 022 to 000.

Final solution

Create the directory first, then use chmod to change the permissions to 777

mkdir('test', 0777);
chmod('test', 0777);

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