Add MacPorts instructions for switching PHP versions

Author: beryllium

downloads-get-instructions.php

@@ -1,12 +1,14 @@
 <?php
 $file = 'unknown';
 $latestPhpVersion = '8.4';
+$priorPhpVersion = '8.3';
 
 if (!isset($options)) {
     $options = [
         'os' => '',
         'usage' => '',
         'version' => '',
+        'priorVersion' => $priorPhpVersion,
     ];
 }
 
@@ -65,6 +67,8 @@
 
 $version = $options['version'];
 $versionNoDot = str_replace('.', '', $version);
+$priorVersion = $options['priorVersion'];
+$priorVersionNoDot = str_replace('.', '', $priorPhpVersion);
 
 if (file_exists(__DIR__ . "/include/download-instructions/{$file}.php")) {
     include __DIR__ . "/include/download-instructions/{$file}.php";

include/download-instructions/osx-macports.php

@@ -4,4 +4,10 @@
 <pre><code class="language-bash line-numbers">
 # Please refer to https://guide.macports.org/chunked/installing.macports.html for installing MacPorts.
 sudo port install php<?= $versionNoDot; ?>
+
+# To install a previous version:
+sudo port install php<?= $priorVersionNoDot; ?>
+
+# To switch to a different version:
+sudo port select php php<?= $priorVersionNoDot; ?>
 </code></pre>