<?php
ini_set('error_reporting', E_ALL);
date_default_timezone_set('Europe/Istanbul');
$dbhost = 'localhost';
$dbname = 'dbname';
$dbuser = 'dbuser';
$dbpass = 'dbpass]';
define("BASE_URL", "http://localhost/");
try {
    $pdo = new PDO("mysql:host={$dbhost};dbname={$dbname}", $dbuser, $dbpass);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
catch( PDOException $ex ) {
    echo "Connection error :" . $ex->getMessage();
}

if(isset($_POST['form1'])) {
    $valid = 1;
    if(empty($_POST['filetoupload'])) {
        $valid = 0;
        $error_message .= "filetoupload alanı boş<br>";
    }
    $path = $_FILES['resim']['name'];
    $path_tmp = $_FILES['resim']['tmp_name'];
    if($path == '') {
        $valid = 0;
        $error_message .= "Resim seçin<br>";
    } else {
        $ext = pathinfo( $path, PATHINFO_EXTENSION );
        $file_name = basename( $path, '.' . $ext );
        if( $ext!='jpg' && $ext!='png' && $ext!='jpeg' && $ext!='gif' ) {
            $valid = 0;
            $error_message .= 'Tur jpg, jpeg, gif ve png Uzantısı Olmalı<br>';
        }
    }
    if($valid == 1) {
        $statement = $pdo->prepare("SHOW TABLE STATUS LIKE 'tbl_resim'");
        $statement->execute();
        $result = $statement->fetchAll();
        foreach($result as $row) {
            $ai_id=$row[10];
        }
        $final_name = 'resim-'.$ai_id.'.'.$ext;
        move_uploaded_file( $path_tmp, '../uploads/'.$final_name );
        $statement = $pdo->prepare("INSERT INTO tbl_resim (filetoupload,name) VALUES (?,?)");
        $statement->execute(array($_POST['filetoupload'],$final_name));
        $success_message = 'Resim yüklendi.';
    }
}
?>
<section class="content">
    <div class="row">
        <div class="col-md-12">
            <?php if($error_message): ?>
            <div class="callout callout-danger">
            <p>
            <?php echo $error_message; ?>
            </p>
            </div>
            <?php endif; ?>
            <?php if($success_message): ?>
            <div class="callout callout-success">
            <p><?php echo $success_message; ?></p>
            </div>
            <?php endif; ?>
            <form class="form-horizontal" action="" method="post" enctype="multipart/form-data">
                <div class="box box-info">
                    <div class="box-body">
                        <div class="form-group">
                            <label for="" class="col-sm-2 control-label">filetoupload<span>*</span></label>
                            <div class="col-sm-4">
                                <input type="text" class="form-control" name="filetoupload">
                            </div>
                        </div>
                        <div class="form-group">
                            <label for="" class="col-sm-2 control-label">Upload Resim <span>*</span></label>
                            <div class="col-sm-4" style="padding-top:6px;">
                                <input type="file" name="resim">
                            </div>
                        </div>
                        <div class="form-group">
                            <label for="" class="col-sm-2 control-label"></label>
                            <div class="col-sm-6">
                                <button type="submit" class="btn btn-success pull-left" name="form1">Submit</button>
                            </div>
                        </div>
                    </div>
                </div>
            </form>
        </div>
    </div>
</section>

bu tek sayfa hali

bu kısmı senin attığın gibi sadece upload.php yapacaksan direk yapıştır form sayfası ayrı ise formun gönder kısmında buton name="form1" yap

if(isset($_POST['form1'])) {
    $valid = 1;
    if(empty($_POST['filetoupload'])) {
        $valid = 0;
        $error_message .= "filetoupload alanı boş<br>";
    }
    $path = $_FILES['resim']['name'];
    $path_tmp = $_FILES['resim']['tmp_name'];
    if($path == '') {
        $valid = 0;
        $error_message .= "Resim seçin<br>";
    } else {
        $ext = pathinfo( $path, PATHINFO_EXTENSION );
        $file_name = basename( $path, '.' . $ext );
        if( $ext!='jpg' && $ext!='png' && $ext!='jpeg' && $ext!='gif' ) {
            $valid = 0;
            $error_message .= 'Tur jpg, jpeg, gif ve png Uzantısı Olmalı<br>';
        }
    }
    if($valid == 1) {
        $statement = $pdo->prepare("SHOW TABLE STATUS LIKE 'tbl_resim'");
        $statement->execute();
        $result = $statement->fetchAll();
        foreach($result as $row) {
            $ai_id=$row[10];
        }
        $final_name = 'resim-'.$ai_id.'.'.$ext;
        move_uploaded_file( $path_tmp, '../uploads/'.$final_name );
        $statement = $pdo->prepare("INSERT INTO tbl_resim (filetoupload,name) VALUES (?,?)");
        $statement->execute(array($_POST['filetoupload'],$final_name));
        $success_message = 'Resim yüklendi.';
    }
}
?>