This code snippet is the basis for restricting content for users in the WordPress Admin

post-editing-restrct.md

##Restrict Post Editing in the WordPress Admin

This code allows any users with the capability to edit other’s posts to view all posts. This means editors and administrators will be able to see all posts. Users with other roles like contributor or authors will only see their own posts. If you are using custom user roles on your site, then you need to keep in mind that users who can edit posts added by other users will also be able to see them.

post-editing-restrct.php

<?php 

function posts_for_current_author($query) {
	global $pagenow;

	if( 'edit.php' != $pagenow || !$query->is_admin )
	    return $query;

	if( !current_user_can( 'edit_others_posts' ) ) {
		global $user_ID;
		$query->set('author', $user_ID );
	}
	return $query;
}
add_filter('pre_get_posts', 'posts_for_current_author');