magento2,blocks,overrides – How to Override Block .php File in Magento 2

To overide block file you need to do this things.

1 – First of all create di.xml file in Folder Company/Extension/etc/di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Sales\Block\Adminhtml\Order\Create\Search\Grid" type="Company\Extension\Block\Adminhtml\Order\Create\Search\Grid" />
</config>

2 – Now create Grid.php Block file in Folder Company\Extension\Block\Adminhtml\Order\Create\Search

<?php
    namespace Company\Extension\Block\Adminhtml\Order\Create\Search;

    class Grid extends \Magento\Sales\Block\Adminhtml\Order\Create\Search\Grid
    {
        // WRITE YOUR FUNCTION TO OVERIDE
    }
?>

You have error in your block file

Vendor/Package/Block/Adminhtml/Group/Edit.Form.php

<?php 
namespace ZeroCool\AdvancedReviews\Block\Adminhtml\Group\Edit;

use Magento\Customer\Controller\RegistryConstants;
//Add "/" in start of extends
 class Form extends \Magento\Customer\Block\Adminhtml\Group\Edit
 {

public function _prepareLayout()
{
    echo "Layout Worked Successfully..."; die();
}

}