diff --git a/sapi/phpdbg/phpdbg_lexer.l b/sapi/phpdbg/phpdbg_lexer.l
index eb159bdef1c7a..6245262a00598 100644
--- a/sapi/phpdbg/phpdbg_lexer.l
+++ b/sapi/phpdbg/phpdbg_lexer.l
@@ -82,7 +82,7 @@ ID          [^ \r\n\t:#\000]+
 GENERIC_ID  ([^ \r\n\t:#\000"']|":\\")+|["]([^\n\000"\\]|"\\\\"|"\\"["])+["]|[']([^\n\000'\\]|"\\\\"|"\\"['])+[']
 ADDR        [0][x][a-fA-F0-9]+
 OPCODE      (ZEND_|zend_)([A-Z_a-z])+
-INPUT       ("\\"[#"']|["]("\\\\"|"\\"["]|[^\n\000"])+["]|[']("\\"[']|"\\\\"|[^\n\000'])+[']|[^\n\000#"'])+
+INPUT       ("\\"[#"']|["]("\\\\"|"\\"["]|[^\n\000"])*["]|[']("\\"[']|"\\\\"|[^\n\000'])*[']|[^\n\000#"'])+
 
 <!*> := yyleng = (size_t) YYCURSOR - (size_t) yytext;
 
diff --git a/sapi/phpdbg/tests/gh16174.phpt b/sapi/phpdbg/tests/gh16174.phpt
new file mode 100644
index 0000000000000..f108cd66be9a2
--- /dev/null
+++ b/sapi/phpdbg/tests/gh16174.phpt
@@ -0,0 +1,10 @@
+--TEST--
+GH-16174 (Empty string is an invalid expression for phpdbg-ev)
+--PHPDBG--
+ev $e = ""
+ev $f = ''
+--EXPECT--
+prompt> 
+prompt> 
+prompt> 
+prompt>