Build complex rules, serialize them as JSON, and execute them in PHP
MIT License
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 JsonLogic.com, 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
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:
Here we're beginning to nest rules.
JWadhams\JsonLogic::apply(
[ "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:
JWadhams\JsonLogic::apply(
[ "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:
JWadhams\JsonLogic::apply(
[ "var" => "a" ],
[ "a" => 1, "b" => 2 ]
);
// 1
You can also use the var
operator to access an array by numeric index:
JWadhams\JsonLogic::apply(
[ "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
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.
//Always
JWadhams\JsonLogic::apply(true, $data_will_be_ignored);
// true
//Never
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 https://raw.githubusercontent.com/jwadhams/json-logic-php/master/src/JWadhams/JsonLogic.php