RFC Idea - is_json - looking for feedback

> Before starting, I want to thank all for taking time from your time, to > give me a feedback, I sincerely respect that, so ... thanks! > > Sorry for the long message, but I have the feeling that ... this is it, is > now ... or it will not be, at least not now, so ... here my best effort; > even though, I dont put aside the possibility that I might have an > offuscated view/opinion regarding my proposal, so is possible that I might > not see the things right ... you know .. I am human after all. > > So, enough of prologue and let's start .... > > # Why would I have code that checks if a json-string is a valid json, if I > will not use the content inside it? (or something like that) > > - Some of you , asked me this question. > - That depends on the infinite amout of use cases that the human brain can > imagine, that is why I say that is not the right approach to discuss this > topic. > > # Why this change then? > > - Is web related, ergo, is PHP related. > - It does not add complexity into PHP, with this functionality we are using > the existing JSON parser that exists in PHP at the moment, the only thing > we do is to create an interface between "userland" and the parser itself, > without the need to use memory as json_decode() is using to check if a > string is a valid json-string or not. > > > ## Proposed functionality (proposed, subject to changes for sure, as now I > have only a working and dirty prototype for this) > > function is_json(string $json, int $flags): bool {} > > Returns: > TRUE if json-string is valid json, otherwise returns FALSE. > > Exceptions: > Optionally set, for the same or subset of exceptions of the actual > json_decode(), like the one Syntax Error for example. > > > So far this is it, subject to changes for sure. > > > # Real open-source project over github using json_decode() just to check if > a json-string is valid ... and nothing else than that. > > - I provide here use cases from major projects, where they ned to have code > that has to be able to check if an string is a valid JSON and nothing else > than that. > - Please check the link to see full code > - I provide here some small snippets from the link I provide > - We are not discussing here how they implemented the code, what I want to > show here is that there is a need to check if an string is a valid > JSON-string without th need to create an object/array out of it. > - Also, we are not discussing if they are mejor projects or not. They are > listed in github as major projects, with stars and a big community of users > and developers maintaining them. > - On some snippets I wrote some notes too, because on some of them is not > obvious how a funciton like the one I propose could be useful. > > > ## Symfony Framework > > https://github.com/symfony/symfony/blob/870eeb975feb1abb4b8a1722e1fd57beeab2b230/src/Symfony/Component/Validator/Constraints/JsonValidator.php > > ``` > class JsonValidator extends ConstraintValidator > ... > ... > ... > ``` > > ## Laravel Framework > > https://github.com/laravel/framework/blob/302a579f00ebcb2573f481054cbeadad9c970605/src/Illuminate/Validation/Concerns/ValidatesAttributes.php > > ``` > public function validateJson($attribute, $value) > { > if (is_array($value)) { > return false; > } > > if (! is_scalar($value) && ! is_null($value) && ! > method_exists($value, '__toString')) { > return false; > } > > json_decode($value); > > return json_last_error() === JSON_ERROR_NONE; > } > ``` > > https://github.com/laravel/framework/blob/61eac9cae4717699ecb3941b16c3d775820d4ca2/src/Illuminate/Support/Str.php > > ``` > public static function isJson($value) > { > ``` > > > ## Magento > > https://github.com/magento/magento2/blob/7c6b6365a3c099509d6f6e6c306cb1821910aab0/app/code/Magento/User/Block/Role/Grid/User.php > > ``` > private function getJSONString($input) > { > $output = json_decode($input); > return $output ? $this->_jsonEncoder->encode($output) : '{}'; > } > ``` > > https://github.com/magento/magento2/blob/7c6b6365a3c099509d6f6e6c306cb1821910aab0/lib/internal/Magento/Framework/DB/DataConverter/SerializedToJson.php > > ``` > protected function isValidJsonValue($value) > { > if (in_array($value, ['null', 'false', '0', '""', '[]']) > || (json_decode($value) !== null && json_last_error() === > JSON_ERROR_NONE) > ) { > return true; > } > //JSON last error reset > json_encode([]); > return false; > } > ``` > > https://github.com/magento/magento2/blob/7c6b6365a3c099509d6f6e6c306cb1821910aab0/lib/internal/Magento/Framework/Serialize/JsonValidator.php > > ``` > public function isValid($string) > { > if ($string !== false && $string !== null && $string !== '') { > json_decode($string); > if (json_last_error() === JSON_ERROR_NONE) { > return true; > } > } > return false; > } > ``` > > ## getgrav > > https://github.com/getgrav/grav/blob/3e7f67f589267e61f823d19824f3ee1b9a8a38ff/system/src/Grav/Common/Data/Validation.php > > ``` > public static function validateJson($value, $params) > { > return (bool) (@json_decode($value)); > } > ``` > > > ## Symfony / http-kernel > > https://github.com/symfony/http-kernel/blob/94986633e4c3e7facb7defbd094a2e1170486ab5/DataCollector/RequestDataCollector.php > > ``` > public function getPrettyJson() > { > $decoded = json_decode($this->getContent()); > //<------ here they decode, just to check if is valid json-string or not, > that is th reason of this line. > > return \JSON_ERROR_NONE === json_last_error() ? > json_encode($decoded, \JSON_PRETTY_PRINT) : null; > } > ``` > > ## Respect / Validation > > https://github.com/Respect/Validation/blob/3dcd859d986f1b586b5539ea19962723ab7352ed/library/Rules/Json.php > > ``` > final class Json extends AbstractRule > { > /** > * {@inheritDoc} > */ > public function validate($input): bool > { > if (!is_string($input) || $input === '') { > return false; > } > > json_decode($input); > > return json_last_error() === JSON_ERROR_NONE; > } > } > ``` > > https://github.com/Respect/Validation/blob/3dcd859d986f1b586b5539ea19962723ab7352ed/library/Rules/Json.php > > ``` > final class Json extends AbstractRule > { > /** > * {@inheritDoc} > */ > public function validate($input): bool > { > if (!is_string($input) || $input === '') { > return false; > } > > json_decode($input); > > return json_last_error() === JSON_ERROR_NONE; > } > } > ``` > > ## humhub > > https://github.com/humhub/humhub/blob/26d7e2667a9317057abe335a056ac8e8f4d675fb/protected/humhub/modules/web/security/controllers/ReportController.php > > > ``` > public function actionIndex() > { > Yii::$app->response->statusCode = 204; > > if(!SecuritySettings::isReportingEnabled()) { > return; > } > > $json_data = file_get_contents('php://input'); > if ($json_data = json_decode($json_data)) { > //<----- here they json_decode() just to check if > is valid json-string only, am I right? > $json_data = json_encode($json_data, JSON_PRETTY_PRINT | > JSON_UNESCAPED_SLASHES); > $json_data = preg_replace('/\'nonce-[^\']*\'/', > "'nonce-xxxxxxxxxxxxxxxxxxxxxxxx'", $json_data); > Yii::error($json_data, 'web.security'); > } > } > ``` > > ## Prestashop > > https://github.com/PrestaShop/PrestaShop/blob/24f9e510ecb0cb002ac3f4834f3210e8d9359899/classes/Validate.php > > ``` > public static function isJson($string) > { > json_decode($string); > > return json_last_error() == JSON_ERROR_NONE; > } > ``` > > > ## Wordpress CLI > > https://github.com/wp-cli/wp-cli/blob/f3e4b0785aa3d3132ee73be30aedca8838a8fa06/php/utils.php > > ``` > function is_json( $argument, $ignore_scalars = true ) { > if ( ! is_string( $argument ) || '' === $argument ) { > return false; > } > > if ( $ignore_scalars && ! in_array( $argument[0], [ '{', '[' ], true ) > ) { > return false; > } > > json_decode( $argument, $assoc = true ); > > return json_last_error() === JSON_ERROR_NONE; > } > ``` > > > ## JOOMLA CMS > > https://github.com/joomla/joomla-cms/blob/09d14c65f25f9bc76f2698e69c4d7b35f43bc848/libraries/src/Form/Field/AccessiblemediaField.php > > ``` > if (\is_string($value)) { > json_decode($value); > //<---------------------------------------------------------- HERE > > // Check if value is a valid JSON string. > if ($value !== '' && json_last_error() !== JSON_ERROR_NONE) { > /** > * If the value is not empty and is not a valid JSON string, > * it is most likely a custom field created in Joomla 3 and > * the value is a string that contains the file name. > */ > if (is_file(JPATH_ROOT . '/' . $value)) { > $value = '{"imagefile":"' . $value . '","alt_text":""}'; > } else { > $value = ''; > } > } > > ``` > > > > # Stackoverflow questions related to this > > ## In PHP, this question is one of the most high ranked questions related > to json && php in stackoverflow, "Fastest way to check if a string is JSON > in PHP?" > > ### The question > > https://stackoverflow.com/questions/6041741/fastest-way-to-check-if-a-string-is-json-in-php > Viewed 484k times > > ### The ranking > > https://stackoverflow.com/questions/tagged/php%20json?sort=MostVotes&edited=true > > ## Person asking how to do exactly this, also providing a real use case; > eventhough in python, the programming language is not important. > > https://stackoverflow.com/questions/5508509/how-do-i-check-if-a-string-is-valid-json-in-python > > ## Someone has also doing exactly this , in JAVA > > https://stackoverflow.com/questions/3679479/check-if-file-is-json-java