How to add file types to my upload script

Hi,

I have the below script to upload files.

I want to only allow specific file type such as jpg png and pdf

can anyone help me add this to my code

thanks

<?php

	if(isset($_FILES['ImageUpload'])) {
		$imageName = $_FILES['ImageUpload']['name'];
		$imageName = mt_rand(100000,999999).$imageName;
		$imageTemp = $_FILES['ImageUpload']['tmp_name'];
		$imageType = $_FILES['ImageUpload']['type'];
		$file_size = $_FILES['ImageUpload']['size'];
		
		$imageName = preg_replace("#[^a-z0-9.]#i", "", $imageName);
		
  		
		if (($file_size > 125000)){      
        echo "File too large. File must be less than 2 megabytes. $file_size";
		die;
		}
	if (!$imageTemp) {
		echo("Nope");
	}else{
		move_uploaded_file($imageTemp, "Upload/$imageName");
	}
}
?>

Edited December 7, 201411 yr by ashleywebdesign