diff --git a/lib/ace/mode/php_highlight_rules.js b/lib/ace/mode/php_highlight_rules.js
index 033671eb..0c0557d6 100644
--- a/lib/ace/mode/php_highlight_rules.js
+++ b/lib/ace/mode/php_highlight_rules.js
@@ -969,7 +969,7 @@ var PhpLangHighlightRules = function() {
                     else if (value == "debugger")
                         return "invalid.deprecated";
                     else
-                        if(value.match(/^(\$[a-zA-Z][a-zA-Z0-9_]*|self|parent)$/))
+                        if(value.match(/^(\$[a-zA-Z_][a-zA-Z0-9_]*|self|parent)$/))
                             return "variable";
                         return "identifier";
                 },