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use Seld\JsonLint\JsonParser;

$parser = new JsonParser();

// returns null if it's valid json, or a ParsingException object.

// Call getMessage() on the exception object to get
// a well formatted error message error like this

// Parse error on line 2:
// ... "key": "value"    "numbers": [1, 2, 3]
// ----------------------^
// Expected one of: 'EOF', '}', ':', ',', ']'

// Call getDetails() on the exception to get more info.

// returns parsed json, like json_decode() does, but slower, throws
// exceptions on failure.

You can also pass additional flags to JsonParser::lint/parse that tweak the functionality:

  • JsonParser::DETECT_KEY_CONFLICTS throws an exception on duplicate keys.
  • JsonParser::ALLOW_DUPLICATE_KEYS collects duplicate keys. e.g. if you have two foo keys they will end up as foo and foo.2.
  • JsonParser::PARSE_TO_ASSOC parses to associative arrays instead of stdClass objects.
  • JsonParser::ALLOW_COMMENTS parses while allowing (and ignoring) inline // and multiline /* */ comments in the JSON document.


$parser = new JsonParser;
try {
    $parser->parse(file_get_contents($jsonFile), JsonParser::DETECT_KEY_CONFLICTS);
} catch (DuplicateKeyException $e) {
    $details = $e->getDetails();
    echo 'Key '.$details['key'].' is a duplicate in '.$jsonFile.' at line '.$details['line'];

Note: This library is meant to parse JSON while providing good error messages on failure. There is no way it can be as fast as php native json_decode().

It is recommended to parse with json_decode, and when it fails parse again with seld/jsonlint to get a proper error message back to the user. See for example how Composer uses this library:


For a quick install with Composer use:

$ composer require seld/jsonlint

JSON Lint can easily be used within another app if you have a PSR-4 autoloader, or it can be installed through Composer for use as a CLI util. Once installed via Composer you can run the following command to lint a json file or URL:

$ bin/jsonlint file.json


  • PHP 5.3+
  • [optional] PHPUnit 3.5+ to execute the test suite (phpunit --version)

Submitting bugs and feature requests

Bugs and feature request are tracked on GitHub


Jordi Boggiano - -


JSON Lint is licensed under the MIT License - see the LICENSE file for details


This library is a port of the JavaScript jsonlint library.