Build complex rules, serialize them as JSON, and execute them in PHP
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Jeremy Wadhams
Jeremy Wadhams Adding substr support
Latest commit 6d38c14 Oct 5, 2017


This parser accepts JsonLogic rules and executes them in PHP.

The JsonLogic format is designed to allow you to share rules (logic) between front-end and back-end code (regardless of language difference), even to store logic along with a record in a database. JsonLogic is documented extensively at, including examples of every supported operation and a place to try out rules in your browser.

The same format can also be executed in JavaScript by the library json-logic-js


A note about types

This is a PHP interpreter of a format designed to be transmitted and stored as JSON. So it makes sense to conceptualize the rules in JSON.

Expressed in JSON, a JsonLogic rule is always one key, with an array of values.

{"==" : ["apples", "apples"]}

PHP has a way to express associative arrays as literals, and no object equivalent, so all these examples are written as if JsonLogic rules were decoded with json_decode's $assoc parameter set true, e.g.

json_decode('{"==" : ["apples", "apples"]}', true);
// ["==" => ["apples", "apples"]]

The library will happily accept either associative arrays or objects:

$rule = '{"==":["apples", "apples"]}';

//Decode the JSON string to an array, and evaluate it.
JWadhams\JsonLogic::apply( json_decode($rule, true) );
// true

//Decode the JSON string to an object, and evaluate it.
JWadhams\JsonLogic::apply( json_decode($rule, false) );
// true


JWadhams\JsonLogic::apply( [ "==" => [1, 1] ] );
// true

This is a simple test, equivalent to 1 == 1. A few things about the format:

  1. The operator is always in the "key" position. There is only one key per JsonLogic rule.
  2. The values are typically an array.
  3. Each value can be a string, number, boolean, array, or null


Here we're beginning to nest rules.

	[ "and" => [
		[ ">" => [3,1] ],
		[ "<" => [1,3] ]
	] ]
// true

In an infix language (like PHP) this could be written as:

( (3 > 1) and (1 < 3) )


Obviously these rules aren't very interesting if they can only take static literal data. Typically JsonLogic::apply will be called with a rule object and a data object. You can use the var operator to get attributes of the data object:

	[ "var" => ["a"] ], // Rule
	[ "a" => 1, "b" => 2 ]   // Data
// 1

If you like, we support syntactic sugar on unary operators to skip the array around values:

	[ "var" => "a" ],
	[ "a" => 1, "b" => 2 ]
// 1

You can also use the var operator to access an array by numeric index:

	[ "var" => 1 ],
	[ "apple", "banana", "carrot" ]
// "banana"

Here's a complex rule that mixes literals and data. The pie isn't ready to eat unless it's cooler than 110 degrees, and filled with apples.

$rules = [ "and" => [
	[ "<" => [ [ "var" => "temp" ], 110 ] ],
	[ "==" => [ [ "var" => "pie.filling" ], "apple" ] ]
] ];

$data = [ "temp" => 100, "pie" => [ "filling" => "apple" ] ];

JWadhams\JsonLogic::apply($rules, $data);
// true

Always and Never

Sometimes the rule you want to process is "Always" or "Never." If the first parameter passed to JsonLogic::apply is a non-object, non-associative-array, it is returned immediately.

JWadhams\JsonLogic::apply(true, $data_will_be_ignored);
// true

JWadhams\JsonLogic::apply(false, $i_wasnt_even_supposed_to_be_here);
// false


The best way to install this library is via Composer:

composer require jwadhams/json-logic-php

If that doesn't suit you, and you want to manage updates yourself, the entire library is self-contained in src/JWadhams/JsonLogic.php and you can download it straight into your project as you see fit.

curl -O