用php更改站点根目录

I want to change the root of my website with php functions.

This is my website (mysite.com)

This website using (current root document) and loading from index.php like this

mysite.com /
  index.php
  folder1
  folder2

now I want when we open (mysite.com) show index.php inside of folder1.(change the root to /folder1/ )

I can use redirect but my address will be like this mysite.com/folder1

but I want this website (mysite.com) using /folder1/ as root directory with out we want to user (mysite.com/folder1)

What should I do? What is the functions for this to use in index.php (to use folder1 as root directory)?

You can use your .htaccess to change the file it default loads:

# Set the startfile to something else:
DirectoryIndex folder1/index.php

Changing basic functionality is a stupid thing to do*. It's confusing, especially for people who are new to the code, or if you look back in a year or so. It will slow down progress and development in the long run. A big no go!*

*Unless you know what you are doing. Which you're not if you have to ask :)

If you are very sure you want to go through with this, you can set the DOCUMENT_ROOT to something else.

// Place this as high as possible in your code, like a config
$_SERVER['DOCUMENT_ROOT'].= '/folder1';

To provide a more professional method, you could change the document_root in the httpd.conf, and have the php $_server value set to the new value serverwide.

Some other Q&As from SO that might help:

How do I change the root directory of an apache server?

how to remove folder name from url using htaccess

This is an excellent fit for .htaccess usage if you can't access the httpd.conf.

RewriteEngine on

# Change yourdomain.com to be your primary domain.
RewriteCond %{HTTP_HOST} ^(www.)?yourprimarydomain.com$

# Change 'subfolder' to be the folder you will use for your primary domain.
RewriteCond %{REQUEST_URI} !^/subfolder/

# Don't change this line.
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_FILENAME} !-d

# Change 'subfolder' to be the folder you will use for your primary domain.
RewriteRule ^(.*)$ /subfolder/$1

# Change yourdomain.com to be your primary domain again. 
# Change 'subfolder' to be the folder you will use for your primary domain 
# followed by / then the main file for your site, index.php, index.html, etc.
RewriteCond %{HTTP_HOST} ^(www.)?yourmaindomain.com$ 
RewriteRule ^(/)?$ subfolder/index.php [L]

If you really want use php, you can place index.php file in you root dir with this content:

<?php
  header('Location: /folder1/');
?>

Althought, better way to do this, is with htaccess.