samlple.php

<?php
require('config.php');
session_start();
if(isset($_POST['submit'])){
     move_uploaded_file($_FILES['file']['tmp_name'],"pictures/".$_FILES['file']['name']);
     mysqli_query($new,"UPDATE users SET picture = '".$_FILES['file']['name']."' WHERE uname = '".$_SESSION['uname']."'");
}
    if($_SESSION['picture'] == ""){
    echo "<img width='100' height='100' src='pictures/bot.png' alt='Default profile pic'>";
}else{
    echo "<img width='100' height='100' src='pictures/".$_SESSION['picture']."'>";
}
?>
<form action="profile.php" method="post" enctype="multipart/form-data">
<input type="file" name="file"> <button type="submit" name="submit">submit</button>
</form>