Stdlib: json_decode()/json_encode() with JSON_THROW_ON_ERROR must throw JsonException (ext/json/php_json.c)

[PurHur]

Category

stdlib · php-src-strict

Problem

When the JSON_THROW_ON_ERROR flag is passed, invalid JSON must throw JsonException (extends Exception). This compiler throws TypeError (or generic errors) instead, so user catch (JsonException $e) handlers never run.

php-src reference

• php/php-src ext/json/php_json.c — php_json_decode_ex, JSON_THROW_ON_ERROR
• php/php-src ext/json/php_json.h — php_json_throw_exception
• php/php-src ext/json/json_encoder.c — encode failures with throw flag

Repro

<?php
try {
    json_decode('{', null, 512, JSON_THROW_ON_ERROR);
    echo "no throw\n";
} catch (JsonException $e) {
    echo "JsonException\n";
} catch (Throwable $e) {
    echo get_class($e), "\n";
}

php repro.php           # Zend: JsonException
php bin/vm.php repro.php # VM today: TypeError

Additional probes (php-src-strict)

json_encode("\xB1\x31", JSON_THROW_ON_ERROR); // invalid UTF-8 → JsonException
json_decode('{"a":}', flags: JSON_THROW_ON_ERROR); // syntax error → JsonException

Scope (PHP-in-PHP)

Path	Work
ext/json/VmJson.php (or ext/standard/)	Map parser/encoder failures to JsonException when JSON_THROW_ON_ERROR set
ext/json/Module.php	Ensure JsonException class registered
lib/JIT/Builtin/	JIT json decode/encode throw path parity when flags are compile-time known
Tests	test/compliance/cases/ext/json_throw_on_error.phpt

Done when

• Invalid json_decode(..., JSON_THROW_ON_ERROR) throws JsonException with catchable type
• json_encode UTF-8 / depth / recursion failures with throw flag throw JsonException
• Without JSON_THROW_ON_ERROR, legacy null + json_last_error() behavior unchanged (php-src-strict)
• ./script/docker-exec.sh -- php bin/vm.php test/compliance/cases/ext/json_throw_on_error.phpt green

[PurHur]

claim: cursor-agent-lane-c — batch (issues #8786, #9026, #9032)

[PurHur]

claim released: cursor-agent-lane-c — verified green on master (2026-06-28); Zend and VM both pass issue repro.

[PurHur]

claim: PHP Compiler Ext — I/O & Crypto — starting this run

[PurHur]

Merged via #18560.

Root cause: Behavior was already implemented on master (VmJsonFormat + json_encode throw paths; JsonException in ThrowableManifest). Issue repro was stale.

Shipped: test/compliance/cases/json/json_throw_on_error.phpt regression guard (decode syntax + encode invalid UTF-8 with JSON_THROW_ON_ERROR).

Verification:

php bin/vm.php test/compliance/cases/json/json_throw_on_error.phpt  # JsonException code=4/5
php bin/jit.php test/compliance/cases/json/json_throw_on_error.phpt # same