为什么这个php文件上传验证脚本不起作用？

Question

Dear friends, this is a script which simply upload file and insert filename into database, why is this not working ? It's just upload the file and send filename to db even after validation . Please help

<?php

//file validation starts
//split filename into array and substract full stop from the last part
$tmp = explode('.', $_FILES['photo']['name']);
$fileext= $tmp[count($tmp)-1];

//read the extension of the file that was uploaded
$allowedexts = array("png");
if(in_array($fileext, $allowedexts)){
    return true;
}else{
    $form_error= "Upload file was not supported<br />";
    header('Location: apply.php?form_error=' .urlencode($form_error));
}


//file validation ends

//upload dir for pics
$uploaddir = './uploads/';


//upload file in folder
$uploadfile = $uploaddir. basename($_FILES['photo']['name']);


//insert filename in mysql db
$upload_filename = basename($_FILES['photo']['name']);



//upload the file now
    move_uploaded_file($_FILES['photo']['tmp_name'], $uploadfile);

// $photo value is goin to db
$photo = $upload_filename;

Answer 1

function send_error($error = 'Unknown error accured')
{
    header('Location: apply.php?form_error=' .urlencode($error));
    exit; //!!!!!!
}
//file validation starts
//split filename into array and substract full stop from the last part

$fileext = end(explode('.', $_FILES['photo']['name'])); //Ricky Dang | end()

//read the extension of the file that was uploaded
$allowedexts = array("png");
if(!in_array($fileext, $allowedexts))
{
}

//upload dir for pics
$uploaddir = './uploads/';
if(!is_dir($uploaddir))
{
    send_error("Upload Directory Error");
}    

//upload file in folder
$uploadfile = $uploaddir. basename($_FILES['photo']['name']);

if(!file_exists($uploadfile ))
{
    send_error("File already exists!");
}

//insert filename in mysql db
$upload_filename = basename($_FILES['photo']['name']);

//upload the file now
if(move_uploaded_file($_FILES['photo']['tmp_name'], $uploadfile))
{
    send_error('Upload Failed, cannot move file!');
}

// $photo value is goin to db
$photo = $upload_filename;

This is a cleared up version to yours, give that a go and see if you get any errors