feature.patch

diff --git a/Zend/tests/unless.phpt b/Zend/tests/unless.phpt
new file mode 100644
index 00000000..f83516a8
--- /dev/null
+++ b/Zend/tests/unless.phpt
@@ -0,0 +1,62 @@
+--TEST--
+unless: Ruby-style negated-if construct (block, else, and statement modifier)
+--FILE--
+<?php
+// Block form: body runs only when the condition is false.
+unless (false) {
+    echo "block-runs\n";
+}
+unless (true) {
+    echo "should-not-print\n";
+}
+
+// else clause.
+unless (true) {
+    echo "should-not-print\n";
+} else {
+    echo "else-runs\n";
+}
+unless (false) {
+    echo "body-runs\n";
+} else {
+    echo "should-not-print\n";
+}
+
+// Statement modifier: `STMT unless COND;`.
+print "modifier-runs\n" unless false;
+print "should-not-print\n" unless true;
+
+// Equivalent to if (!cond) across values.
+foreach ([1, 0, -1] as $x) {
+    unless ($x > 0) {
+        echo "nonpos:$x\n";
+    }
+}
+
+// Semi-reserved: still usable as a method/const name.
+class C {
+    const unless = "const-ok";
+    function unless() { return "method-ok"; }
+}
+echo (new C)->unless(), "\n";
+echo C::unless, "\n";
+
+// Exposed to the tokenizer.
+var_dump(in_array(
+    "T_UNLESS",
+    array_map("token_name", array_column(token_get_all("<?php unless(true){}"), 0)),
+    true
+));
+var_dump(defined("T_UNLESS"));
+?>
+--EXPECT--
+block-runs
+else-runs
+body-runs
+modifier-runs
+nonpos:0
+nonpos:-1
+method-ok
+const-ok
+bool(true)
+bool(true)
diff --git a/Zend/tests/unless_comprehensive.phpt b/Zend/tests/unless_comprehensive.phpt
new file mode 100644
index 00000000..e06bf004
--- /dev/null
+++ b/Zend/tests/unless_comprehensive.phpt
@@ -0,0 +1,41 @@
+--TEST--
+unless — block, else, modifier, truthiness, nesting, semi-reserved
+--FILE--
+<?php
+// block form
+unless (false) { echo "runs when false\n"; }
+unless (true)  { echo "should NOT run\n"; }
+// else
+unless (in_array(3, [1,2])) { echo "no 3\n"; } else { echo "has 3\n"; }
+unless (in_array(2, [1,2])) { echo "no 2\n"; } else { echo "has 2\n"; }
+// statement modifier
+$dry = false;
+print "saved\n" unless $dry;
+$dry = true;
+print "not-printed-when-dry\n" unless $dry;
+// truthiness parity with if(!...)
+unless (0) { echo "0 is falsy\n"; }
+unless ("") { echo "empty string falsy\n"; }
+unless ([]) { echo "empty array falsy\n"; }
+unless ("0") { echo "string zero is falsy too\n"; }
+// nesting + short-circuit
+function side(): bool { echo "side()\n"; return true; }
+unless (true && side()) { echo "no\n"; }   // side() runs
+unless (false) { unless (false) { echo "nested\n"; } }
+// semi-reserved: usable as a method/const name
+class C { const unless = 42; function unless() { return "method"; } }
+echo C::unless, "\n";
+echo (new C)->unless(), "\n";
+--EXPECT--
+runs when false
+no 3
+has 2
+saved
+0 is falsy
+empty string falsy
+empty array falsy
+string zero is falsy too
+side()
+nested
+42
+method
diff --git a/Zend/zend_language_parser.y b/Zend/zend_language_parser.y
index e4d61006..cb53111a 100644
--- a/Zend/zend_language_parser.y
+++ b/Zend/zend_language_parser.y
@@ -116,6 +116,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %token <ident> T_CLONE         "'clone'"
 %token <ident> T_EXIT          "'exit'"
 %token <ident> T_IF            "'if'"
+%token <ident> T_UNLESS        "'unless'"
 %token <ident> T_ELSEIF        "'elseif'"
 %token <ident> T_ELSE          "'else'"
 %token <ident> T_ENDIF         "'endif'"
@@ -273,6 +274,7 @@ static YYSIZE_T zend_yytnamerr(char*, const char*);
 %type <ast> alt_if_stmt for_cond_exprs for_exprs switch_case_list global_var_list static_var_list
 %type <ast> echo_expr_list unset_variables catch_name_list catch_list optional_variable parameter_list class_statement_list
 %type <ast> implements_list case_list if_stmt_without_else
+%type <ast> unless_stmt unless_stmt_without_else unless_modifier
 %type <ast> non_empty_parameter_list argument_list non_empty_argument_list property_list
 %type <ast> class_const_list class_const_decl class_name_list trait_adaptations method_body non_empty_for_exprs
 %type <ast> ctor_arguments alt_if_stmt_without_else trait_adaptation_list lexical_vars
@@ -306,7 +308,7 @@ start:
 
 reserved_non_modifiers:
 	  T_INCLUDE | T_INCLUDE_ONCE | T_EVAL | T_REQUIRE | T_REQUIRE_ONCE | T_LOGICAL_OR | T_LOGICAL_XOR | T_LOGICAL_AND
-	| T_INSTANCEOF | T_NEW | T_CLONE | T_EXIT | T_IF | T_ELSEIF | T_ELSE | T_ENDIF | T_ECHO | T_DO | T_WHILE | T_ENDWHILE
+	| T_INSTANCEOF | T_NEW | T_CLONE | T_EXIT | T_IF | T_UNLESS | T_ELSEIF | T_ELSE | T_ENDIF | T_ECHO | T_DO | T_WHILE | T_ENDWHILE
 	| T_FOR | T_ENDFOR | T_FOREACH | T_ENDFOREACH | T_DECLARE | T_ENDDECLARE | T_AS | T_TRY | T_CATCH | T_FINALLY
 	| T_THROW | T_USE | T_INSTEADOF | T_GLOBAL | T_VAR | T_UNSET | T_ISSET | T_EMPTY | T_CONTINUE | T_GOTO
 	| T_FUNCTION | T_CONST | T_RETURN | T_PRINT | T_YIELD | T_LIST | T_SWITCH | T_ENDSWITCH | T_CASE | T_DEFAULT | T_BREAK
@@ -510,6 +512,8 @@ statement:
 		'{' inner_statement_list '}' { $$ = $2; }
 	|	if_stmt { $$ = $1; }
 	|	alt_if_stmt { $$ = $1; }
+	|	unless_stmt { $$ = $1; }
+	|	unless_modifier { $$ = $1; }
 	|	T_WHILE '(' expr ')' while_statement
 			{ $$ = zend_ast_create(ZEND_AST_WHILE, $3, $5); }
 	|	T_DO statement T_WHILE '(' expr ')' ';'
@@ -789,6 +793,30 @@ alt_if_stmt:
 			      zend_ast_create(ZEND_AST_IF_ELEM, NULL, $4)); }
 ;
 
+/* `unless (C) S` desugars to `if (!C) S` by emitting the same IF/IF_ELEM AST
+ * with the condition wrapped in a boolean-NOT node. No compiler changes needed. */
+unless_stmt_without_else:
+		T_UNLESS '(' expr ')' statement
+			{ $$ = zend_ast_create_list(1, ZEND_AST_IF,
+			      zend_ast_create(ZEND_AST_IF_ELEM,
+			          zend_ast_create_ex(ZEND_AST_UNARY_OP, ZEND_BOOL_NOT, $3), $5)); }
+;
+
+unless_stmt:
+		unless_stmt_without_else %prec T_NOELSE { $$ = $1; }
+	|	unless_stmt_without_else T_ELSE statement
+			{ $$ = zend_ast_list_add($1, zend_ast_create(ZEND_AST_IF_ELEM, NULL, $3)); }
+;
+
+/* Statement modifier: `STMT unless COND;` (Ruby style). The left expression
+ * runs unless the condition holds, i.e. `if (!COND) STMT`. */
+unless_modifier:
+		expr T_UNLESS expr ';'
+			{ $$ = zend_ast_create_list(1, ZEND_AST_IF,
+			      zend_ast_create(ZEND_AST_IF_ELEM,
+			          zend_ast_create_ex(ZEND_AST_UNARY_OP, ZEND_BOOL_NOT, $3), $1)); }
+;
+
 parameter_list:
 		non_empty_parameter_list possible_comma { $$ = $1; }
 	|	%empty	{ $$ = zend_ast_create_list(0, ZEND_AST_PARAM_LIST); }
diff --git a/Zend/zend_language_scanner.l b/Zend/zend_language_scanner.l
index 3ecb2f8d..697c2a32 100644
--- a/Zend/zend_language_scanner.l
+++ b/Zend/zend_language_scanner.l
@@ -1454,6 +1454,10 @@ OPTIONAL_WHITESPACE_OR_COMMENTS ({WHITESPACE}|{MULTI_LINE_COMMENT}|{SINGLE_LINE_
 	RETURN_TOKEN_WITH_IDENT(T_IF);
 }
 
+<ST_IN_SCRIPTING>"unless" {
+	RETURN_TOKEN_WITH_IDENT(T_UNLESS);
+}
+
 <ST_IN_SCRIPTING>"elseif" {
 	RETURN_TOKEN_WITH_IDENT(T_ELSEIF);
 }