diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 5d12f9684c..5c2b524fcf 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -2101,7 +2101,7 @@ function bump_topic_allowed($forum_id, $topic_bumped, $last_post_time, $topic_po
 function get_context($text, $words, $length = 400)
 {
 	// first replace all whitespaces with single spaces
-	$text = preg_replace('/\s+/', ' ', $text);
+	$text = preg_replace('/\s+/u', ' ', $text);
 
 	$word_indizes = array();
 	if (sizeof($words))
diff --git a/phpBB/includes/message_parser.php b/phpBB/includes/message_parser.php
index c2c700e1c5..797c2f5cfd 100644
--- a/phpBB/includes/message_parser.php
+++ b/phpBB/includes/message_parser.php
@@ -89,7 +89,7 @@ class bbcode_firstpass extends bbcode
 			$this->message = str_replace("\r\n", "\n", $this->message);
 
 			// We strip newlines and spaces after and before quotes in quotes (trimming)
-			$this->message = preg_replace(array('#\[quote(=".*?")?\]([\s|\n]+)#is', '#([\s|\n]+)\[\/quote\]#is'), array("[quote\\1]", "[/quote]"), $this->message);
+			$this->message = preg_replace(array('#\[quote(=".*?")?\]([\s|\n]+)#ius', '#([\s|\n]+)\[\/quote\]#ius'), array("[quote\\1]", "[/quote]"), $this->message);
 
 			// Now we add exactly one newline
 			$this->message = preg_replace(array('#\[quote(=".*?")?\]#is', '#\[\/quote\]#is'), array("[quote\\1]\n", "\n[/quote]"), $this->message);
@@ -445,7 +445,7 @@ class bbcode_firstpass extends bbcode
 					}
 
 					$code = preg_replace('#^<span class="[a-z]+"><span class="([a-z]+)">(.*)</span></span>#s', '<span class="$1">$2</span>', $code);
-					$code = preg_replace('#(?:[\n\r\s\t]|&nbsp;)*</span>$#', '</span>', $code);
+					$code = preg_replace('#(?:[\n\r\s\t]|&nbsp;)*</span>$#u', '</span>', $code);
 
 					// remove newline at the end
 					if (!empty($code) && $code{strlen($code)-1} == "\n")
@@ -933,14 +933,14 @@ class parse_message extends bbcode_firstpass
 		// Do some general 'cleanup' first before processing message,
 		// e.g. remove excessive newlines(?), smilies(?)
 		// Transform \r\n and \r into \n
-		$match = array('#\r\n?#', "#([\n][\s]+){3,}#", '#(script|about|applet|activex|chrome):#i');
+		$match = array('#\r\n?#', "#([\n][\s]+){3,}#u", '#(script|about|applet|activex|chrome):#i');
 		$replace = array("\n", "\n\n", "\\1&#058;");
 		$this->message = preg_replace($match, $replace, trim($this->message));
 
 		// Message length check. -1 disables this check completely.
 		if ($config['max_' . $mode . '_chars'] != -1)
 		{
-			$msg_len = ($mode == 'post') ? utf8_strlen($this->message) : utf8_strlen(preg_replace('#\[\/?[a-z\*\+\-]+(=[\S]+)?\]#is', ' ', $this->message));
+			$msg_len = ($mode == 'post') ? utf8_strlen($this->message) : utf8_strlen(preg_replace('#\[\/?[a-z\*\+\-]+(=[\S]+)?\]#ius', ' ', $this->message));
 	
 			if ((!$msg_len && $mode !== 'sig') || $config['max_' . $mode . '_chars'] && $msg_len > $config['max_' . $mode . '_chars'])
 			{
diff --git a/phpBB/includes/search/fulltext_mysql.php b/phpBB/includes/search/fulltext_mysql.php
index 09e9162d83..8a102a321d 100644
--- a/phpBB/includes/search/fulltext_mysql.php
+++ b/phpBB/includes/search/fulltext_mysql.php
@@ -116,7 +116,7 @@ class fulltext_mysql extends search_backend
 
 		if ($terms == 'all')
 		{
-			$match		= array('#\sand\s#i', '#\sor\s#i', '#\snot\s#i', '#\+#', '#-#', '#\|#');
+			$match		= array('#\sand\s#iu', '#\sor\s#iu', '#\snot\s#iu', '#\+#', '#-#', '#\|#');
 			$replace	= array(' +', ' |', ' -', ' +', ' -', ' |');
 
 			$keywords = preg_replace($match, $replace, $keywords);
diff --git a/phpBB/includes/search/fulltext_native.php b/phpBB/includes/search/fulltext_native.php
index 07ebfc6047..df000f5e04 100755
--- a/phpBB/includes/search/fulltext_native.php
+++ b/phpBB/includes/search/fulltext_native.php
@@ -173,7 +173,7 @@ class fulltext_native extends search_backend
 		{
 			$words = array();
 
-			preg_match_all('#([^\\s+\\-|()]+)(?:$|[\\s+\\-|()])#', $keywords, $words);
+			preg_match_all('#([^\\s+\\-|()]+)(?:$|[\\s+\\-|()])#u', $keywords, $words);
 			if (sizeof($words[1]))
 			{
 				$keywords = '(' . implode('|', $words[1]) . ')';
@@ -184,7 +184,7 @@ class fulltext_native extends search_backend
 		$this->search_query = $keywords;
 
 		$exact_words = array();
-		preg_match_all('#([^\\s+\\-|*()]+)(?:$|[\\s+\\-|()])#', $keywords, $exact_words);
+		preg_match_all('#([^\\s+\\-|*()]+)(?:$|[\\s+\\-|()])#u', $keywords, $exact_words);
 		$exact_words = $exact_words[1];
 
 		if (sizeof($exact_words))
diff --git a/phpBB/search.php b/phpBB/search.php
index f8fa502839..f504f2079a 100644
--- a/phpBB/search.php
+++ b/phpBB/search.php
@@ -130,7 +130,7 @@ if ($keywords || $author || $author_id || $search_id || $submit)
 		else
 		{
 			$search_terms = 'all';
-			$keywords = implode(' |', explode(' ', preg_replace('#\s+#', ' ', $keywords))) . ' ' .$add_keywords;
+			$keywords = implode(' |', explode(' ', preg_replace('#\s+#u', ' ', $keywords))) . ' ' .$add_keywords;
 		}
 	}
 
@@ -447,7 +447,7 @@ if ($keywords || $author || $author_id || $search_id || $submit)
 
 	// define some vars for urls
 	// @todo preg_replace still needed?
-	$hilit = preg_replace('#&amp;(\#[0-9]+;)#', '&$1', htmlspecialchars(implode('|', explode(' ', preg_replace('#\s+#', ' ', str_replace(array('+', '-', '|', '(', ')'), ' ', $keywords))))));
+	$hilit = htmlspecialchars(implode('|', explode(' ', preg_replace('#\s+#u', ' ', str_replace(array('+', '-', '|', '(', ')'), ' ', $keywords)))));
 	$u_hilit = urlencode($keywords);
 	$u_show_results = ($show_results != 'posts') ? '&amp;sr=' . $show_results : '';
 	$u_search_forum = implode('&amp;fid%5B%5D=', $search_forum);