Question

when I run the below code, I got error “Fatal error: Call to undefined function posix_getpwuid()” in line $owner = posix_getpwuid($uid);.

1. why?
2. does that means there’s no owner when $uid=0?

I know that $uid=0

$logfile = 'log.txt';
    echo substr(sprintf('%o', fileperms($logfile)), -4)."<br />";
    $uid = fileowner($logfile);
    if ($uid === false) die("Could not determine file owner!");
    $owner = posix_getpwuid($uid);
    echo "The file owner's name is " . $owner[name] . "\r\n";

Answer 1

The error means exactly what it says: There is no such function posix_getpwuid().

However, since there obviously is, POSIX functions must be disabled on your server. Contact your host to find out if this is the case and why.

I believe a UID of 0 indicates the root user, but I don’t know enough about filesystems to know for sure.