Trying to upload image type files only.

Hello,

I am trying to prevent my form, from submitting if the file is not an image type file but i keep failing, the array that i am using keeps displaying regardless of the files type.
Any help would be grateful.

<?php

    $Manufacturer = $_POST['Manufacturer'];
    $Brand = $_POST['Brand'];
    $Model = $_POST['Model'];
    $Type = $_POST['Type'];
    $Wheel = $_POST['Wheels'];
    $Colour = $_POST['Colour'];
    $Number = $_POST['Gears'];
    $Brake = $_POST['Brakes'];
    $Suspension = $_POST['Suspension'];
    $Gender = $_POST['Gender'];
    $Age = $_POST['Ageof'];
    $image = $_FILES["images"]["name"];
    $Additional = $_POST['Additional'];

    include "../include/config.php";
    $upload_folder = "./uploads/";

    $result=mysqli_query($connection,"SELECT * FROM `Bike` WHERE manufacturer='$Manufacturer'");
    //$file="./uploads/".$_FILES["images"]["name"];
    //$image = addslashes(file_get_contents($_FILES . '../BikeRegistrationDAO.php'));

    if($row=mysqli_num_rows($result) > 0){

        echo "This Bicycle's Manufacturer, Is already registered.";
            return;
    }

    $allowed = array("jpg", "jpeg", "png", "gif");

    if (array($allowed !== "jpg", "jpeg", "png", "gif"))
    {
       die("Not a gif/jpeg/png");
    }

    foreach($_FILES["images"]["name"] as $key => $file_name)
    {
        $tmp_name = $_FILES["images"]["tmp_name"][$key];

        if(file_exists ($upload_folder.$file_name))
        {
            echo "The file ". $file_name . " already exists". "</br>";
        }else{
            move_uploaded_file($tmp_name, $upload_folder.$file_name." MPN: ".$Manufacturer); // uploads the image file name to the folder with the bikes MPN number next to it !
            echo "The file " . $file_name . " has successfully uploaded". "</br>";
        } 
    } 

$sql = "INSERT INTO Bike (Manufacturer, Brand, Model, Type, Wheel, Colour, Number, Brake, Suspension, Gender, Age, image, Additional) VALUES ('$Manufacturer', '$Brand', '$Model', '$Type', '$Wheel', '$Colour', '$Number', '$Brake', '$Suspension', '$Gender', '$Age', '$image', '$Additional')";

    if(!mysqli_query($connection, $sql))
    {
        echo "Not Submited";

    }else{

        echo "Submitted Successfully"."</br>";
    } 
?>