diff --git a/lib/ace/mode/php_highlight_rules.js b/lib/ace/mode/php_highlight_rules.js
index 750c90cc..2765a4d2 100644
--- a/lib/ace/mode/php_highlight_rules.js
+++ b/lib/ace/mode/php_highlight_rules.js
@@ -524,7 +524,7 @@ PhpHighlightRules = function() {
                         "OG(?:10E|2E))|PI(?:_(?:2|4)|)|SQRT(?:1_2|2)))|N(?:EGATIVE_SIGN|O(?:EXPR|STR)|_(?:CS_PRECEDES|S(?:EP_BY_SPACE|IGN_POSN)))|" +
                         "P(?:ATH(?:INFO_(?:BASENAME|DIRNAME|EXTENSION)|_SEPARATOR)|M_STR|OSITIVE_SIGN|_(?:CS_PRECEDES|S(?:EP_BY_SPACE|IGN_POSN)))|" +
                         "RADIXCHAR|S(?:EEK_(?:CUR|END|SET)|ORT_(?:ASC|DESC|NUMERIC|REGULAR|STRING)|TR_PAD_(?:BOTH|LEFT|RIGHT))|" +
-                        "T(?:HOUS(?:ANDS_SEP|EP)|_FMT(?:_AMPM|))|YES(?:EXPR|STR))\\b"
+                        "T(?:HOUS(?:ANDS_SEP|EP)|_FMT(?:_AMPM|))|YES(?:EXPR|STR)|STD(?:IN|OUT|ERR))\\b"
             }, {
                 token : function(value) {
                     if (keywords[value])