Json Path 语法

JSONPath

This is a JSONPath implementation for PHP based on Stefan Goessner's JSONPath script.

JSONPath is an XPath-like expression language for filtering, flattening and extracting data.

I believe that is improves on the original script (which was last updated in 2007) by doing a few things:

• Object-oriented code (should be easier to manage or extend in future)
• Expressions are parsed into tokens using some code cribbed from Doctrine Lexer and cached
• There is no eval() in use
• Performance is pretty much the same
• Any combination of objects/arrays/ArrayAccess-objects can be used as the data input which is great if you're de-serializing JSON in to objects
  or if you want to process your own data structures.

JSONPath Examples

JSONPath	Result
$.store.books[*].author	the authors of all books in the store
$..author	all authors
$.store..price	the price of everything in the store.
$..books[2]	the third book
$..books[(@.length-1)]	the last book in order.
$..books[0,1]	the first two books
$..books[:2]	the first two books
$..books[?(@.isbn)]	filter all books with isbn number
$..books[?(@.price<10)]	filter all books cheapier than 10
$..*	all elements in the data (recursively extracted)

Expression syntax

Symbol	Description
$	The root object/element (not strictly necessary)
@	The current object/element
. or []	Child operator
..	Recursive descent
*	Wildcard. All child elements regardless their index.
[,]	Array indices as a set
[start:end:step]	Array slice operator borrowed from ES4/Python.
?()	Filters a result set by a script expression
()	Uses the result of a script expression as the index

PHP Usage

$data = ['people' => [['name' => 'Joe'], ['name' => 'Jane'], ['name' => 'John']]];
$result = (new JSONPath($data))->find('$.people.*.name'); // returns new JSONPath
// $result[0] === 'Joe'
// $result[1] === 'Jane'
// $result[2] === 'John'

Magic method access

The options flag JSONPath::ALLOW_MAGIC will instruct JSONPath when retrieving a value to first check if an object
has a magic __get() method and will call this method if available. This feature is iffy and
not very predictable as:

• wildcard and recursive features will only look at public properties and can't smell which properties are magically accessible
• there is no property_exists check for magic methods so an object with a magic __get() will always return true when checking
  if the property exists
• any errors thrown or unpredictable behaviour caused by fetching via __get() is your own problem to deal with

$jsonPath = new JSONPath($myObject, JSONPath::ALLOW_MAGIC);

For more examples, check the JSONPathTest.php tests file.

Script expressions

Script expressions are not supported as the original author intended because:

• This would only be achievable through eval (boo).
• Using the script engine from different languages defeats the purpose of having a single expression evaluate the same way in different
  languages which seems like a bit of a flaw if you're creating an abstract expression syntax.

So here are the types of query expressions that are supported:

[?(@._KEY_ _OPERATOR_ _VALUE_)] // <, >, !=, and ==
Eg.
[?(@.title == "A string")] //
[?(@.title = "A string")]
// A single equals is not an assignment but the SQL-style of '=='

Similar projects

JMESPath does similiar things, is full of features and has a PHP implementation

The Hash utility from CakePHP does some similar things

The original JsonPath implementations is available at http://code.google.com/p/jsonpath and re-hosted for composer
here Peekmo/JsonPath.

ObjectPath (https://github.com/adriank/ObjectPath) appears to be a Python/JS implementation
with a new name and extra features.

Changelog

0.3.0

• Added JSONPathToken class as value object
• Lexer clean up and refactor
• Updated the lexing and filtering of the recursive token ("..") to allow for a combination of recursion
  and filters, eg. $..[?(@.type == 'suburb')].name

0.2.1 - 0.2.5

• Various bug fixes and clean up

0.2.0

• Added a heap of array access features for more creative iterating and chaining possibilities

0.1.x

• Init