preserve runtime integer division semantics

src/CompilerBase.php

@@ -3047,6 +3047,13 @@ class CompilerBase implements PropertyAccessContext
                         if ($evaluation !== null && is_float($evaluation['result'])) {
                             return Type::FLOAT;
                         }
+                        // Runtime integer division has a value-dependent PHP
+                        // result: exact quotients are int, fractional quotients
+                        // and PHP_INT_MIN / -1 are float. Keep it boxed when the
+                        // operands are not compile-time constants.
+                        if ($exprType === 'Expr_BinaryOp_Div' && $evaluation === null) {
+                            return Type::VAR;
+                        }
                     }
                 }
                 if ($leftType === Type::INT || $rightType === Type::INT) {

src/Optimizer/SsaTypeOptimizer.php

@@ -318,7 +318,7 @@ trait SsaTypeOptimizer
      */
     protected function exprCanOverflowInt(NodeAbstract $expr): bool
     {
-        // Division always produces float in PHP when operands are int
+        // Runtime division may produce float even when both operands are int.
         if ($expr instanceof Node\Expr\BinaryOp\Div) {
             return true;
         }

src/Parser/BinaryOpTrait.php

@@ -158,20 +158,20 @@ trait BinaryOpTrait
         }
 
         // Declared int parameters use the native Int ABI even in ordinary PHP
-        // mode. A direct C++ +/−/* would therefore have undefined signed
+        // mode. Direct C++ +/−/* can overflow, while C++ integer division
-        // overflow, while PHP promotes the result to float. Route dynamic
+        // truncates and cannot raise PHP's DivisionByZeroError. Route dynamic
         // integer arithmetic through the encapsulated Variant operators unless
         // the user explicitly selected `use native_types`. Fully constant
         // expressions remain safe to emit directly after the checks above.
         if (!$this->nativeTypes
             && $leftType === Type::INT
             && $rightType === Type::INT
-            && in_array($op, ['+', '-', '*'], true)
+            && in_array($op, ['+', '-', '*', '/'], true)
             && $this->evaluateConstantIntArithmetic($left, $right, $op) === null
         ) {
             // Keep the potentially widening result boxed, but pass the native
-            // RHS directly so PHPX can use its inline checked-int overload
+            // RHS directly so PHPX can use its inline checked arithmetic
-            // without constructing and destroying another temporary zval.
+            // overload without constructing and destroying another zval.
             return '((php::Var(' . $leftExpr . ')) ' . $op . ' (' . $rightExpr . '))';
         }
 

tests/compiler/operator/runtime-int-division.phpt

@@ -0,0 +1,50 @@
+--TEST--
+Runtime int division preserves PHP exact, fractional, overflow and zero-divisor semantics
+--FILE--
+<?php
+declare(strict_types=1);
+
+function divide(int $left, int $right): mixed
+{
+    return $left / $right;
+}
+
+function divide_assign(int $left, int $right): mixed
+{
+    $result = $left;
+    $result /= $right;
+    return $result;
+}
+
+function main(): void
+{
+    var_dump(divide(12, 3));
+    var_dump(divide(10, 4));
+    var_dump(divide(PHP_INT_MIN, -1));
+
+    var_dump(divide_assign(12, 3));
+    var_dump(divide_assign(10, 4));
+    var_dump(divide_assign(PHP_INT_MIN, -1));
+
+    try {
+        divide(10, 0);
+    } catch (DivisionByZeroError $error) {
+        echo "divide by zero\n";
+    }
+
+    try {
+        divide_assign(10, 0);
+    } catch (DivisionByZeroError $error) {
+        echo "divide assign by zero\n";
+    }
+}
+?>
+--EXPECT--
+int(4)
+float(2.5)
+float(9.223372036854776E+18)
+int(4)
+float(2.5)
+float(9.223372036854776E+18)
+divide by zero
+divide assign by zero