php中某处未定义的偏移量错误的日期和时间错误

I am making a program for updating the database and by the time I clicked the update button it displays an error like this:

Notice: Undefined offset: 2 in C:\xampp\htdocs\maritime_database\students_entry.php on line 103

Notice: Undefined offset: 1 in C:\xampp\htdocs\maritime_database\students_entry.php on line 103

it is somewhere in the line 103 and this is the code:

<?php

if($opr=="upd")
{
    $sql_upd=mysql_query("SELECT * FROM students WHERE stud_id=$id");
    $rs_upd=mysql_fetch_array($sql_upd);
    list($y,$m,$d)=explode('-',$rs_upd['dob']);
?>

Why you parse date manually ? PHP has date built-in function :

<?php
 if($opr=="upd"){
    $sql_upd = mysql_query("SELECT * FROM students WHERE stud_id=$id");
    $rs_upd = mysql_fetch_array($sql_upd);
    $dob = strtotime($rs_upd['dob']); // Convert into UNIX time
    $y = date("Y",$dob); // Extract Year
    $m = date("m",$dob); // Extract Month
    $d = date("d",$dob); // Extract Day
    echo "Day : ".$d."
";
    echo "Month : ".$m."
";
    echo "Year : ".$y."
";
 }
?>