Encode non-BMP UTF-8 characters as HTML entities

common/functions.php

@@ -5,3 +5,19 @@
  * 
  * Copyright (c) Rhymix Developers and Contributors
  */
+
+/**
+ * Encode UTF-8 characters outside of the Basic Multilingual Plane in the &#xxxxxx format.
+ * This allows emoticons and other characters to be stored in MySQL without utf8mb4 support.
+ * 
+ * @param $str The string to encode
+ * @return string
+ */
+function utf8_mbencode($str)
+{
+	return preg_replace_callback('/[\xF0-\xF7][\x80-\xBF]{3}/', function($m) {
+		$bytes = array(ord($m[0][0]), ord($m[0][1]), ord($m[0][2]), ord($m[0][3]));
+		$codepoint = ((0x07 & $bytes[0]) << 18) + ((0x3F & $bytes[1]) << 12) + ((0x3F & $bytes[2]) << 6) + (0x3F & $bytes[3]);
+		return '&#x' . dechex($codepoint) . ';';
+	}, $str);
+}