A library to validate a json schema.

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6.0.0-beta 2024-07-09 07:19 UTC


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A PHP Implementation for validating JSON Structures against a given Schema with support for Schemas of Draft-3 or Draft-4. Features of newer Drafts might not be supported. See Table of All Versions of Everything to get an overview of all existing Drafts.

See json-schema for more details.



git clone https://github.com/jsonrainbow/json-schema.git


Install PHP Composer

composer require justinrainbow/json-schema


For a complete reference see Understanding JSON Schema.

Note: features of Drafts newer than Draft-4 might not be supported!

Basic usage


$data = json_decode(file_get_contents('data.json'));

// Validate
$validator = new JsonSchema\Validator;
$validator->validate($data, (object)['$ref' => 'file://' . realpath('schema.json')]);

if ($validator->isValid()) {
    echo "The supplied JSON validates against the schema.\n";
} else {
    echo "JSON does not validate. Violations:\n";
    foreach ($validator->getErrors() as $error) {
        printf("[%s] %s\n", $error['property'], $error['message']);

Type coercion

If you're validating data passed to your application via HTTP, you can cast strings and booleans to the expected types defined by your schema:


use JsonSchema\SchemaStorage;
use JsonSchema\Validator;
use JsonSchema\Constraints\Factory;
use JsonSchema\Constraints\Constraint;

$request = (object)[

    $request, (object) [
); // validates!

is_bool($request->processRefund); // true
is_int($request->refundAmount); // true

A shorthand method is also available:

$validator->coerce($request, $schema);
// equivalent to $validator->validate($data, $schema, Constraint::CHECK_MODE_COERCE_TYPES);

Default values

If your schema contains default values, you can have these automatically applied during validation:


use JsonSchema\Validator;
use JsonSchema\Constraints\Constraint;

$request = (object)[

$validator = new Validator();

); //validates, and sets defaults for missing properties

is_bool($request->processRefund); // true
$request->processRefund; // true

With inline references


use JsonSchema\SchemaStorage;
use JsonSchema\Validator;
use JsonSchema\Constraints\Factory;

$jsonSchema = <<<'JSON'
    "type": "object",
    "properties": {
        "data": {
            "oneOf": [
                { "$ref": "#/definitions/integerData" },
                { "$ref": "#/definitions/stringData" }
    "required": ["data"],
    "definitions": {
        "integerData" : {
            "type": "integer",
            "minimum" : 0
        "stringData" : {
            "type": "string"

// Schema must be decoded before it can be used for validation
$jsonSchemaObject = json_decode($jsonSchema);

// The SchemaStorage can resolve references, loading additional schemas from file as needed, etc.
$schemaStorage = new SchemaStorage();

// This does two things:
// 1) Mutates $jsonSchemaObject to normalize the references (to file://mySchema#/definitions/integerData, etc)
// 2) Tells $schemaStorage that references to file://mySchema... should be resolved by looking in $jsonSchemaObject
$schemaStorage->addSchema('file://mySchema', $jsonSchemaObject);

// Provide $schemaStorage to the Validator so that references can be resolved during validation
$jsonValidator = new Validator(new Factory($schemaStorage));

// JSON must be decoded before it can be validated
$jsonToValidateObject = json_decode('{"data":123}');

// Do validation (use isValid() and getErrors() to check the result)
$jsonValidator->validate($jsonToValidateObject, $jsonSchemaObject);

Configuration Options

A number of flags are available to alter the behavior of the validator. These can be passed as the third argument to Validator::validate(), or can be provided as the third argument to Factory::__construct() if you wish to persist them across multiple validate() calls.

Flag Description
Constraint::CHECK_MODE_NORMAL Validate in 'normal' mode - this is the default
Constraint::CHECK_MODE_TYPE_CAST Enable fuzzy type checking for associative arrays and objects
Constraint::CHECK_MODE_COERCE_TYPES Convert data types to match the schema where possible
Constraint::CHECK_MODE_EARLY_COERCE Apply type coercion as soon as possible
Constraint::CHECK_MODE_APPLY_DEFAULTS Apply default values from the schema if not set
Constraint::CHECK_MODE_ONLY_REQUIRED_DEFAULTS When applying defaults, only set values that are required
Constraint::CHECK_MODE_EXCEPTIONS Throw an exception immediately if validation fails
Constraint::CHECK_MODE_DISABLE_FORMAT Do not validate "format" constraints
Constraint::CHECK_MODE_VALIDATE_SCHEMA Validate the schema as well as the provided document

Please note that using CHECK_MODE_COERCE_TYPES or CHECK_MODE_APPLY_DEFAULTS will modify your original data.

CHECK_MODE_EARLY_COERCE has no effect unless used in combination with CHECK_MODE_COERCE_TYPES. If enabled, the validator will use (and coerce) the first compatible type it encounters, even if the schema defines another type that matches directly and does not require coercion.

Running the tests

composer test                            # run all unit tests
composer testOnly TestClass              # run specific unit test class
composer testOnly TestClass::testMethod  # run specific unit test method
composer style-check                     # check code style for errors
composer style-fix                       # automatically fix code style errors