title: upgrade to PHP 8 using Homebrew Error on macOS Big Sur
body: <p>I want to upgrade to PHP 8 with Homebrew on Mac (macOS Big Sur Version: 11.2)
  But there is a problem!</p>
  <p>1- Show my version of PHP:</p>
  <pre><code>TERMINAL:
  MyUser@MacBook-Pro ~ % php -v
  WARNING: PHP is not recommended
  PHP is included in macOS for compatibility with legacy software.
  Future versions of macOS will not include PHP.
  PHP 7.3.24-(to be removed in future macOS) (cli) (built: Dec 21 2020 21:33:25) ( NTS )
  Copyright (c) 1997-2018 The PHP Group
  Zend Engine v3.3.24, Copyright (c) 1998-2018 Zend Technologies
  </code></pre>
  <p>2- Install version 8 of PHP:</p>
  <pre><code>MyUser@MacBook-Pro ~ % brew install shivammathur/php/php@8.0
  Warning: shivammathur/php/php 8.0.2 is already installed, it's just not linked.
  To link this version, run:
  brew link php
  </code></pre>
  <p>3- Brew Link PHP:</p>
  <pre><code>MyUser@MacBook-Pro ~ % brew link --overwrite --force php@8.0
  Error: Formulae found in multiple taps:
      * shivammathur/php/php@5.6
      * exolnet/deprecated/php@5.6
  
  Please use the fully-qualified name (e.g. shivammathur/php/php@5.6) to refer to the formula.
  </code></pre>
  <p><strong>How to solve this problem?</strong></p>