supports old PHP versions

Author: ddrv

composer.json

@@ -25,7 +25,8 @@
     "autoload": {
         "psr-4": {
             "Ddrv\\Mailer\\": "src/"
-        }
+        },
+        "files": ["fn/fn.php"]
     },
     "autoload-dev": {
         "psr-4": {

fn/fn.php

@@ -0,0 +1,62 @@
+<?php
+
+if (!function_exists('mb_str_split')) {
+    function mb_str_split($string, $split_length = 1, $encoding = null)
+    {
+        if (
+            null !== $string
+            && !is_scalar($string)
+            && !(is_object($string)
+            && method_exists($string, '__toString'))
+        ) {
+            trigger_error(
+                'mb_str_split(): expects parameter 1 to be string, ' . gettype($string) . ' given',
+                E_USER_WARNING
+            );
+            return null;
+        }
+        if (null !== $split_length && !is_bool($split_length) && !is_numeric($split_length)) {
+            trigger_error(
+                'mb_str_split(): expects parameter 2 to be int, ' . gettype($split_length) . ' given',
+                E_USER_WARNING
+            );
+            return null;
+        }
+        $split_length = (int) $split_length;
+        if (1 > $split_length) {
+            trigger_error('mb_str_split(): The length of each segment must be greater than zero', E_USER_WARNING);
+            return false;
+        }
+        if (null === $encoding) {
+            $encoding = mb_internal_encoding();
+        } else {
+            $encoding = (string) $encoding;
+        }
+
+        if (!in_array($encoding, mb_list_encodings(), true)) {
+            static $aliases;
+            if ($aliases === null) {
+                $aliases = array();
+                foreach (mb_list_encodings() as $encoding) {
+                    $encoding_aliases = mb_encoding_aliases($encoding);
+                    if ($encoding_aliases) {
+                        foreach ($encoding_aliases as $alias) {
+                            $aliases[] = $alias;
+                        }
+                    }
+                }
+            }
+            if (! in_array($encoding, $aliases, true)) {
+                trigger_error('mb_str_split(): Unknown encoding "' . $encoding . '"', E_USER_WARNING);
+                return null;
+            }
+        }
+
+        $result = array();
+        $length = mb_strlen($string, $encoding);
+        for ($i = 0; $i < $length; $i += $split_length) {
+            $result[] = mb_substr($string, $i, $split_length, $encoding);
+        }
+        return $result;
+    }
+}