diff --git a/src/CompilerBase.php b/src/CompilerBase.php
index 2fabe604..7ed87a33 100644
--- a/src/CompilerBase.php
+++ b/src/CompilerBase.php
@@ -2144,6 +2144,19 @@ class CompilerBase implements PropertyAccessContext
             $returnType = Type::VAR;
         }
 
+        if (!$this->context->inClosure
+            && ($type === Type::VAR || $type === Type::REF)
+            && $this->isStrictScalarType($returnType)) {
+            // Keep the zval type until the declared return boundary has been
+            // checked. Converting first would silently coerce invalid values.
+            $tmpVar = $this->addTmpVar(Type::VAR);
+            $code = $tmpVar . ' = (' . $expr . ');' . PHP_EOL;
+            $code .= $this->genStrictScalarReturnCheck($tmpVar, $returnType);
+            $code .= $this->getIndent() . 'return '
+                . $this->convertExprType($tmpVar, $returnType, Type::VAR) . ';';
+            return $code;
+        }
+
         $returnObjectCheckClass = '';
         // 返回值的表达式是一个类的对象
         $objectClass = $this->detectDeclaredClassOfExpr($v->expr);
diff --git a/src/Generator/CallArgumentGenerator.php b/src/Generator/CallArgumentGenerator.php
index 8fd214b4..aef054cc 100644
--- a/src/Generator/CallArgumentGenerator.php
+++ b/src/Generator/CallArgumentGenerator.php
@@ -103,7 +103,8 @@ trait CallArgumentGenerator
                 continue;
             }
             $argInfo = $this->getArgInfo($arg, $nativeFunc, $i);
-            $argList[] = $this->getTypeConvertedArg($arg, $argInfo);
+            $callableName = $functionDef->displayName ?: $functionDef->getNamespacedName();
+            $argList[] = $this->getTypeConvertedArg($arg, $argInfo, $callableName, $i);
         }
 
         return implode(', ', $argList);
diff --git a/src/Generator/TypeCheckGenerator.php b/src/Generator/TypeCheckGenerator.php
index 66dbb2e2..fc8ea15b 100644
--- a/src/Generator/TypeCheckGenerator.php
+++ b/src/Generator/TypeCheckGenerator.php
@@ -19,6 +19,87 @@ use PhpParser\NodeAbstract;
 
 trait TypeCheckGenerator
 {
+    protected function isStrictScalarType(string $type): bool
+    {
+        return in_array($type, [Type::INT, Type::FLOAT, Type::BOOL, Type::STR], true);
+    }
+
+    protected function strictScalarTypeName(string $type): string
+    {
+        return match ($type) {
+            Type::INT => 'int',
+            Type::FLOAT => 'float',
+            Type::BOOL => 'bool',
+            Type::STR => 'string',
+            default => throw new \LogicException('Not a strict scalar type: ' . $type),
+        };
+    }
+
+    protected function genStrictScalarCondition(string $valueExpr, string $type): string
+    {
+        return match ($type) {
+            Type::INT => $valueExpr . '.isInt()',
+            // PHP permits int values at a float boundary even in strict mode.
+            Type::FLOAT => '(' . $valueExpr . '.isFloat() || ' . $valueExpr . '.isInt())',
+            Type::BOOL => $valueExpr . '.isBool()',
+            Type::STR => $valueExpr . '.isString()',
+            default => throw new \LogicException('Not a strict scalar type: ' . $type),
+        };
+    }
+
+    protected function genStrictScalarParamCheck(
+        ArgInfo $argInfo,
+        string $valueExpr,
+        string $callableName,
+        string $argNoExpr
+    ): string {
+        if (!$this->isStrictScalarType($argInfo->type)) {
+            return '';
+        }
+
+        $paramName = $argInfo->phpName ?: $this->unescapeVarName($argInfo->name);
+        $format = $this->genCharPtr($callableName . '(): Argument #', true)
+            . ' ZEND_LONG_FMT '
+            . $this->genCharPtr(
+                ' ($' . $paramName . ') must be of type ' . $this->strictScalarTypeName($argInfo->type)
+                    . ', %s given',
+                true
+            );
+        $throwExpr = 'php::throwExceptionEx(zend_ce_type_error, 0, ' . $format . ', '
+            . $argNoExpr . ', ' . $valueExpr . '.typeStr())';
+
+        $code = $this->getIndent() . 'if (UNEXPECTED(!('
+            . $this->genStrictScalarCondition($valueExpr, $argInfo->type) . '))) {' . PHP_EOL;
+        $this->indentLevel++;
+        $code .= $this->getIndent() . $throwExpr . ';' . PHP_EOL;
+        $this->indentLevel--;
+        $code .= $this->getIndent() . '}' . PHP_EOL;
+        return $code;
+    }
+
+    protected function genStrictScalarReturnCheck(string $valueExpr, string $returnType): string
+    {
+        if (!$this->isStrictScalarType($returnType)) {
+            return '';
+        }
+
+        $fnName = $this->getTypeCheckCallableName();
+        $format = $this->genCharPtr(
+            $fnName . '(): Return value must be of type ' . $this->strictScalarTypeName($returnType)
+                . ', %s returned',
+            true
+        );
+
+        $code = $this->getIndent() . 'if (UNEXPECTED(!('
+            . $this->genStrictScalarCondition($valueExpr, $returnType) . '))) {' . PHP_EOL;
+        $this->indentLevel++;
+        $code .= $this->getIndent() . 'php::throwExceptionEx(zend_ce_type_error, 0, '
+            . $format . ', ' . $valueExpr . '.typeStr());' . PHP_EOL;
+        $this->indentLevel--;
+        $code .= $this->getIndent() . '}' . PHP_EOL;
+        return $code;
+    }
+
     protected function buildTypeCheckFromNode(NodeAbstract $typeNode): array
     {
         $check = [];
diff --git a/src/Translator.php b/src/Translator.php
index 52b80885..98de0baf 100644
--- a/src/Translator.php
+++ b/src/Translator.php
@@ -3176,7 +3176,15 @@ CODE;
                 $cppCode .= $this->getIndent() . Type::ARRAY . ' ' . $var . ';' . PHP_EOL;
                 $cppCode .= $this->getIndent() . 'for (uint32_t i = ' . $k . '; i < php::getCallArgNum(); i++) {' . PHP_EOL;
                 $this->indentLevel++;
-                $cppCode .= $this->getIndent() . $var . '.append(php::getCallArg(i));' . PHP_EOL;
+                if ($this->isStrictScalarType($argInfo->type)) {
+                    $rawVar = 'raw_' . $var;
+                    $cppCode .= $this->getIndent() . Type::VAR . ' ' . $rawVar . ' = php::getCallArg(i);' . PHP_EOL;
+                    $cppCode .= $this->genStrictScalarParamCheck($argInfo, $rawVar, $displayName, 'i + 1');
+                    $cppCode .= $this->getIndent() . $var . '.append('
+                        . $this->convertExprFromType($argInfo->type, $rawVar) . ');' . PHP_EOL;
+                } else {
+                    $cppCode .= $this->getIndent() . $var . '.append(php::getCallArg(i));' . PHP_EOL;
+                }
                 $this->indentLevel--;
                 $cppCode .= '}' . PHP_EOL;
                 $cppCode .= $this->genExtraNamedVariadicArgs($var);
@@ -3200,7 +3208,17 @@ CODE;
                 }
                 $cppType = $this->getDefaultArgumentType($argInfo);
                 $declaredClass = $argInfo->declaredClass ?: $argInfo->class;
-                if ($argInfo->type === Type::OBJECT && $declaredClass !== '') {
+                if ($this->isStrictScalarType($argInfo->type)) {
+                    $rawVar = 'raw_' . $var;
+                    $cppCode .= $this->getIndent() . Type::VAR . ' ' . $rawVar . ' = ' . $argExpr . ';' . PHP_EOL;
+                    $cppCode .= $this->genStrictScalarParamCheck(
+                        $argInfo,
+                        $rawVar,
+                        $displayName,
+                        (string) ($k + 1)
+                    );
+                    $expr = $this->convertExprFromType($argInfo->type, $rawVar);
+                } elseif ($argInfo->type === Type::OBJECT && $declaredClass !== '') {
                     $expr = $this->convertObjectExpr($argExpr, $this->getClassEntryPtr($declaredClass));
                 } else {
                     $expr = $this->convertExprFromType($argInfo->type, $argExpr);
diff --git a/src/TypeSystem/NativeTypeCompatibilityTrait.php b/src/TypeSystem/NativeTypeCompatibilityTrait.php
index 1d08660c..89fe0ca7 100644
--- a/src/TypeSystem/NativeTypeCompatibilityTrait.php
+++ b/src/TypeSystem/NativeTypeCompatibilityTrait.php
@@ -139,7 +139,12 @@ trait NativeTypeCompatibilityTrait
         return false;
     }
 
-    protected function getTypeConvertedArg(Node\Arg $arg, ArgInfo $argInfo): string
+    protected function getTypeConvertedArg(
+        Node\Arg $arg,
+        ArgInfo $argInfo,
+        string $callableName = '',
+        int $argIndex = 0
+    ): string
     {
         $type = $this->detectTypeOfExpr($arg->value);
         $this->assertExprCanBeUsedAsValue($arg->value, 'function argument');
@@ -180,6 +185,20 @@ trait NativeTypeCompatibilityTrait
         $expr = $this->parseOrderedArg($arg);
         $expr = $this->materializeCallArgValue($arg->value, $expr);
 
+        if (($type === Type::VAR || $type === Type::REF) && $this->isStrictScalarType($argInfo->type)) {
+            // A native scalar ABI value has already lost its zval type. Preserve
+            // the dynamic value until strict_types validation has completed.
+            $tmpVar = $this->addTmpVar(Type::VAR);
+            $this->context->beforeStmtLines[] = $tmpVar . ' = (' . $expr . ');';
+            $this->context->beforeStmtLines[] = rtrim($this->genStrictScalarParamCheck(
+                $argInfo,
+                $tmpVar,
+                $callableName,
+                (string) ($argIndex + 1)
+            ));
+            $expr = $tmpVar;
+        }
+
         $this->checkVarAssignExpr($arg, $argInfo->type, $type);
 
         if ($argInfo->type === Type::VAR && $this->isVarExpr($arg->value)) {
@@ -215,4 +234,3 @@ trait NativeTypeCompatibilityTrait
     }
 
 }
-
diff --git a/tests/compiler/strict_types/scalar-dynamic-boundaries.phpt b/tests/compiler/strict_types/scalar-dynamic-boundaries.phpt
new file mode 100644
index 00000000..9a1ce6bc
--- /dev/null
+++ b/tests/compiler/strict_types/scalar-dynamic-boundaries.phpt
@@ -0,0 +1,71 @@
+--TEST--
+strict scalar declarations validate dynamic parameter and return values
+--ENV--
+USE_ZEND_ALLOC=0
+--FILE--
+<?php
+
+declare(strict_types=1);
+
+function acceptsInt(int $value): int { return $value; }
+function acceptsFloat(float $value): float { return $value; }
+function acceptsBool(bool $value): bool { return $value; }
+function acceptsString(string $value): string { return $value; }
+
+function invalidIntReturn(): int { return json_decode('"bad"'); }
+function invalidFloatReturn(): float { return json_decode('"bad"'); }
+function invalidBoolReturn(): bool { return json_decode('1'); }
+function invalidStringReturn(): string { return json_decode('1'); }
+function widenedFloatReturn(): float { return json_decode('7'); }
+
+function main(): void
+{
+    $string = json_decode('"bad"');
+    $integer = json_decode('1');
+
+    try { acceptsInt($string); echo "int-param=accepted\n"; }
+    catch (TypeError $error) { echo "int-param=TypeError\n"; }
+    try { acceptsFloat($string); echo "float-param=accepted\n"; }
+    catch (TypeError $error) { echo "float-param=TypeError\n"; }
+    try { acceptsBool($integer); echo "bool-param=accepted\n"; }
+    catch (TypeError $error) { echo "bool-param=TypeError\n"; }
+    try { acceptsString($integer); echo "string-param=accepted\n"; }
+    catch (TypeError $error) { echo "string-param=TypeError\n"; }
+
+    try { invalidIntReturn(); echo "int-return=accepted\n"; }
+    catch (TypeError $error) { echo "int-return=TypeError\n"; }
+    try { invalidFloatReturn(); echo "float-return=accepted\n"; }
+    catch (TypeError $error) { echo "float-return=TypeError\n"; }
+    try { invalidBoolReturn(); echo "bool-return=accepted\n"; }
+    catch (TypeError $error) { echo "bool-return=TypeError\n"; }
+    try { invalidStringReturn(); echo "string-return=accepted\n"; }
+    catch (TypeError $error) { echo "string-return=TypeError\n"; }
+
+    $dynamicCall = 'acceptsInt';
+    try { $dynamicCall($string); echo "dynamic-param=accepted\n"; }
+    catch (TypeError $error) { echo "dynamic-param=TypeError\n"; }
+
+    var_dump(acceptsInt(json_decode('7')));
+    var_dump(acceptsFloat(json_decode('1.5')));
+    var_dump(acceptsFloat(json_decode('7')));
+    var_dump(acceptsBool(json_decode('true')));
+    var_dump(acceptsString(json_decode('"ok"')));
+    var_dump(widenedFloatReturn());
+}
+?>
+--EXPECT--
+int-param=TypeError
+float-param=TypeError
+bool-param=TypeError
+string-param=TypeError
+int-return=TypeError
+float-return=TypeError
+bool-return=TypeError
+string-return=TypeError
+dynamic-param=TypeError
+int(7)
+float(1.5)
+float(7)
+bool(true)
+string(2) "ok"
+float(7)