update readme

README.md

@@ -4,7 +4,7 @@ This library provides simple way to interact with Ethereum ERC20 token.
 By default, supports all ERC20 Standard functions (like balanceOf, transfer, transferFrom, approve, allowance, decimal, name, ...) also can be extends to support other contracts as well.
 
 ## Installation
-`composer require ...`
+`composer require lessmore92/php-erc20`
 
 ## Usage
 There are two ways to use:
@@ -57,3 +57,47 @@ $tether = new \Lessmore92\Ethereum\Token("0xdac17f958d2ee523a2206206994597c13d83
 ## Ethereum RPC Client
 For connect to Ethereum blockchain you need an Ethereum node; [Infura](https://infura.io/) is a simple and fast solution, however you can launch you [Geth](https://geth.ethereum.org/) node
 
+
+## ERC20 Token `transferFrom`
+ERC20 transaction fee needs to be paid in `ETH`. In some situation your app needs to pay this fee behalf of user.  
+Suppose, user A have a key pair (private, public) and all their transaction is limited to usdt. User A needs to send 10 usdt, but he/she haven't ETH to pay transaction fee.  
+In these cases your app should pay fee behalf of users.      
+`transferFrom` is a good solution in these cases.
+
+
+## `transferFrom` Flow:
+1.First `approve` grants permissions to a delegator.  
+2.Use `transferFrom` method to make transaction behalf of user. 
+
+*In Action*
+```
+$owner_private = '0xcf29c83a88e23d0b9e676beca426490bf79aca71e9d24f79a99d30c48292e1e3';
+$owner_address = '0xA7e5F270c27E9d33911EE7D50D8E814f793d2760';
+
+$myapp_private = '0xa6b6be193bfeac6160178ee6e1435609ae566a9054715e0802e4c3b39bb94e83';
+$myapp_address = '0x8dC9b3c20795815aa063FEdBE8E564566CEc1893';
+
+$to_address = '0x245013F05DdA116142Ca8db205ec4F8C780E3DcB';
+
+//by this method we allow $myapp_address to send upto 99999 token behalf of $owner_address
+$approve_tx    = $token->approve($owner_address, $myapp_address, 99999);
+$approve_tx_id = $approve_tx->sign($owner_private)
+                            ->send()
+;
+
+
+//the magic is here, $myapp_address send 10 tokens behalf of user and $myapp_address pay transaction fee
+$transfer_tx    = $token->transferFrom($myapp_address, $owner_address, $to_address, 10);
+$transfer_tx_id = $transfer_tx->sign($myapp_private)
+                              ->send()
+;
+
+```
+
+### `allowance` to check how much transferFrom remain
+
+`$remain = $token->allowance($owner_address, $myapp_address);`
+
+*Notices:*  
+`approve` method not need to be used on every transaction.  
+To revoke `transferFrom` permission call `$token->approve($owner_address, $myapp_address, 0)` by amount `0`.