How to resize image in PHP with new dimensions?

Question

Can anyone help me resize an image in core php. Can anyone write code for me to resize an image using core php. Here is my code:

public function add_images(){
        $image=$_FILES['file'];
        if(!empty($image)){
            if($image['error']==0){
                $imgName = pathinfo($_FILES['file']['name']);
                $ext = $imgName['extension'];
                $rand=mt_rand(5,1000000000).'.'.$ext;
                $destination = base_path() . '/public/images/ListingImages/';
                if(move_uploaded_file($image['tmp_name'], $destination.$rand)){
                    echo "moved"; die; 
                }
            }
        }
}

This code works fine for me. But when the user uploads an image it should be resized to 300x300.