<?php

function fileExtension($x){$i = pathinfo($x);return $i['extension'];}

if ($_POST) {
    // Ben güvenlik kontrolü yapmıyorum sen yap
    $file = $_FILES['file'];
    $newName = rand(0, 9999999) . '-image.' . fileExtension($file['name']);
    $upload = move_uploaded_file($file['tmp_name'], 'upload/' . $newName);
    if ($upload) {
        echo "<img src='upload/{$newName}' />"
    } else {
        echo "hata var";
    }
}

?>
<form action="" method="post" enctype="multipart/form-data">
    Dosya seçin: <input type="file" name="file"> <button type="submit">Ekle</button>
</form>