Fix various compatibility issues with PHP 8

libs/ical/Util/ComponentUtil.php

@@ -0,0 +1,62 @@
+<?php
+
+/*
+ * This file is part of the eluceo/iCal package.
+ *
+ * (c) Markus Poerschke <markus@eluceo.de>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Eluceo\iCal\Util;
+
+class ComponentUtil
+{
+    /**
+     * Folds a single line.
+     *
+     * According to RFC 5545, all lines longer than 75 characters should be folded
+     *
+     * @see https://tools.ietf.org/html/rfc5545#section-5
+     * @see https://tools.ietf.org/html/rfc5545#section-3.1
+     *
+     * @param string $string
+     *
+     * @return array
+     */
+    public static function fold($string)
+    {
+        $lines = [];
+
+        if (function_exists('mb_strcut')) {
+            while (strlen($string) > 0) {
+                if (strlen($string) > 75) {
+                    $lines[] = mb_strcut($string, 0, 75, 'utf-8');
+                    $string = ' ' . mb_strcut($string, 75, strlen($string), 'utf-8');
+                } else {
+                    $lines[] = $string;
+                    $string = '';
+                    break;
+                }
+            }
+        } else {
+            $array = preg_split('/(?<!^)(?!$)/u', $string);
+            $line = '';
+            $lineNo = 0;
+            foreach ($array as $char) {
+                $charLen = strlen($char);
+                $lineLen = strlen($line);
+                if ($lineLen + $charLen > 75) {
+                    $line = ' ' . $char;
+                    ++$lineNo;
+                } else {
+                    $line .= $char;
+                }
+                $lines[$lineNo] = $line;
+            }
+        }
+
+        return $lines;
+    }
+}