User Contributed Notes

msaladna at apisnetworks dot com 21-Sep-2017 03:55
Careful when using is_link() in thread-safe builds with the self-referential directory entry ".". On ZTS builds is_link("/home/symlink/.") will return true whereas it returns false on non-ZTS builds.
gggeek 18-Sep-2013 08:53
On windows, take care that is_link returns false for Junctions.
Ways of telling apart a directory from a junction include doing both a stat() and and lstat() call and checking if there is any difference in the results
PaulE 02-Jun-2009 02:03
A workaround for Windows LNK files:

<?php

function _is_link($filename)
{
    if(is_link($filename))
        return true;

    $ext = substr(strrchr($filename, '.'), 1);
    if(strtolower($ext) == 'lnk')
    {
        return (_readlink($filename) ? true : false);
    }

    return false;
}

function _readlink($file)
{
    if(file_exists($file))
    {
        if(is_link($file))
        {
            return readlink($file);
        }

        // Get file content
        $handle = fopen($file, "rb");
        $buffer = array();

        while(!feof($handle))
        {
            $buffer[] = fread($handle, 1);
        }

        fclose($handle);

        // Test magic value and GUID
        if(count($buffer) < 20)
            return false;
        if($buffer[0] != 'L')
            return false;
        if((ord($buffer[4]) != 0x01) ||
           (ord($buffer[5]) != 0x14) ||
           (ord($buffer[6]) != 0x02) ||
           (ord($buffer[7]) != 0x00) ||
           (ord($buffer[8]) != 0x00) ||
           (ord($buffer[9]) != 0x00) ||
           (ord($buffer[10]) != 0x00) ||
           (ord($buffer[11]) != 0x00) ||
           (ord($buffer[12]) != 0xC0) ||
           (ord($buffer[13]) != 0x00) ||
           (ord($buffer[14]) != 0x00) ||
           (ord($buffer[15]) != 0x00) ||
           (ord($buffer[16]) != 0x00) ||
           (ord($buffer[17]) != 0x00) ||
           (ord($buffer[18]) != 0x00) ||
           (ord($buffer[19]) != 0x46))
        {
            return false;
        }

        $i = 20;
        if(count($buffer) < ($i + 4))
            return false;

        $flags = ord($buffer[$i]);
        $flags = $flags | (ord($buffer[++$i]) << 8);
        $flags = $flags | (ord($buffer[++$i]) << 16);
        $flags = $flags | (ord($buffer[++$i]) << 24);

        $hasShellItemIdList = ($flags & 0x00000001) ? true : false;
        $pointsToFileOrDir = ($flags & 0x00000002) ? true : false;

        if(!$pointsToFileOrDir)
            return false;

        if($hasShellItemIdList)
        {
            $i = 76;
            if(count($buffer) < ($i + 2))
                return false;

            $a = ord($buffer[$i]);
            $a = $a | (ord($buffer[++$i]) << 8);
           
        }

        $i = 78 + 4 + $a;
        if(count($buffer) < ($i + 4))
            return false;

        $b = ord($buffer[$i]);
        $b = $b | (ord($buffer[++$i]) << 8);
        $b = $b | (ord($buffer[++$i]) << 16);
        $b = $b | (ord($buffer[++$i]) << 24);

        $i = 78 + $a + $b;
        if(count($buffer) < ($i + 4))
            return false;

        $c = ord($buffer[$i]);
        $c = $c | (ord($buffer[++$i]) << 8);
        $c = $c | (ord($buffer[++$i]) << 16);
        $c = $c | (ord($buffer[++$i]) << 24);

        $i = 78 + $a + $b + $c;
        if(count($buffer) < ($i +1))
            return false;

        $linkedTarget = "";
        for(;$i < count($buffer); ++$i)
        {
            if(!ord($buffer[$i]))
                break;

            $linkedTarget .= $buffer[$i];
        }

        if(empty($linkedTarget))
            return false;

       
        return $linkedTarget;
    }

    return false;
}

if(_is_link('test.lnk'))
{
    echo _readlink('test.lnk');
}
?>
foobarfarter 18-Oct-2008 03:06
@radon8472 at hotmail dot com
The windows .lnk-things are real files, the explorer only treats them like links. Try to open one with Win+R->"notepad X:\Path\Visiblefilename.lnk You will see much 0-Bytes, but the linked path is displayed right on the screen. It should be possible to do the same by php.
radon8472 at hotmail dot com 31-Jul-2008 09:38
This function returns "false" for windows *.lnk files (tested under windows XP).

filetype also returns "file" an not "link" like expected.

I didn`t find a solution for this.
mbirth at webwriters dot de 20-May-2008 08:24
To find out whether a file is hardlinked to another filename, check the number of links of the stat() output. If it is >1 there is another filename for that file.

To find out whether two filenames are pointing to the same file, check the inode number of those 2 filenames. If it is equal, the 2 filenames are hardlinked together.
neverpanic->gmail[com] 30-Dec-2006 02:50
For me (Debian Sarge VPS) is_link returns true even for directories if you don't add a trailing slash to the filename.
<?php
if ($dir{strlen($dir)-1} == '/') $dir = substr($dir, 0, -1);
is_link($dir);
?>
This works for me. It can't detect a symlink somewhere in a complete path, though (i.e. is_link(/www/somedir/file.php) will return false, just as is_link(/www/) would)
brendy at gmail dot com 05-May-2006 07:22
On Mac OSX, to see if a file is a FInder alias:

<?PHP
if( getFinderAlias( $someFile , $target ) ) {
 echo $target;
}
else {
 echo "File is not an alias";
}

function getFinderAlias( $filename , &$target ) {
$getAliasTarget = <<< HEREDOC
    -- BEGIN APPLESCRIPT --
    set checkFileStr to "{$filename}"
    set checkFile to checkFileStr as POSIX file
    try
        tell application "Finder"
            if original item of file checkFile exists then
                set targetFile to (original item of file checkFile) as alias
                set posTargetFile to POSIX path of targetFile as text
                get posTargetFile
            end if
        end tell
    end try
    -- END APPLESCRIPT --
HEREDOC;
$runText = "osascript << EOS\n{$getAliasTarget}\nEOS\n";
$target = trim( shell_exec( $runText ) );
return ( $target == "" ? false : true );
}
?>
andudi at gmx dot ch 02-Jun-2002 10:44
On my SuSE 7.2 is_link does not work on directories, but to find out, if a dir is a link, I use now this:

$linkdir = $path.$linkdirname;
if (realpath($linkdir) != realpath($path)."/".$linkdirname):
//$linkdir is a symbolic linked dir!
...

and this works fine :-)

Andreas Dick