json-logic-php

If you need a rule that always evaluates to true or false, you can pass a boolean literal as the first argument to JWadhams\JsonLogic::apply(). If the first parameter is not an object or an associative array, the library returns it immediately without evaluating the data object.

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

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

You can install the library using Composer, which is the recommended method:

composer require jwadhams/json-logic-php

Alternatively, you can manually download the self-contained library file from the repository and include it in your project:

curl -O https://raw.githubusercontent.com/jwadhams/json-logic-php/master/src/JWadhams/JsonLogic.php

The if and ?: operators implement a conditional branching pattern. They expect an odd number of parameters (3 or greater).

Pattern: if( condition1, result1, condition2, result2, ..., [else_result] )

1. The engine evaluates pairs of (condition, result).
2. If a condition evaluates to truthy, the corresponding result is evaluated and returned immediately (short-circuiting).
3. If the last parameter is provided without a preceding condition, it acts as the else block.
4. If no conditions match and no else is provided, it returns null.

// if(condition, then, else)
$logic = ['if' => [['==' => [1, 1]], 'yes', 'no']];
JsonLogic::apply($logic); // returns 'yes'

// if(cond1, res1, cond2, res2, else)
$logic = ['if' => [['==' => [1, 2]], 'a', ['==' => [1, 1]], 'b', 'c']];
JsonLogic::apply($logic); // returns 'b'

The var operator allows you to retrieve values from the $data array passed to apply(). It supports dot-notation for descending into nested arrays or objects.

• Dot-notation: Use strings like 'user.profile.name' to traverse the data structure.
• Default values: You can provide a second argument to var to return a default value if the path is not found or is empty.
• Root access: If var is called with null or an empty string, it returns the entire $data object/array.

// Example of dot-notation access
$logic = ['var' => 'user.age'];
$data = ['user' => ['age' => 25]];

$result = JsonLogic::apply($logic, $data);
// $result is 25

The primary way to execute logic is using the JWadhams\JsonLogic::apply() method. This method accepts a rule (as an associative array or object) and an optional data object.

Rules are structured as associative arrays where the key is the operator and the value is an array of operands. The library supports both associative arrays (decoded via json_decode($json, true)) and objects (decoded via json_decode($json, false)).

// Using an associative array rule
JWadhams\JsonLogic::apply([ "==" => [1, 1] ]);

// Using a JSON string rule (decoded as object)
$rule = '{"==":["apples", "apples"]}';
JWadhams\JsonLogic::apply(json_decode($rule, false));

You can add your own operators to the engine using JsonLogic::add_operation($name, $callable).

• $name: A string representing the operator key used in the JSON logic.
• $callable: A PHP callable (function, closure, etc.) that accepts the arguments extracted from the logic rule and returns a result.

Custom operations are executed during the apply() process if no built-in operator matches the provided name.

JsonLogic::add_operation('is_even', function($n) {
    return $n % 2 === 0;
});

$logic = ['is_even' => [['var' => 'number']]];
$data = ['number' => 4];

$result = JsonLogic::apply($logic, $data);
// $result is true

The primary way to use this library is via the JsonLogic::apply($logic, $data) method. It evaluates a JSON Logic rule against a provided data set.

• $logic: The rule to evaluate. It can be an associative array (e.g., ['==' => [1, 1]]), an object (which will be cast to an array), or an array of multiple logic statements.
• $data: The data context used by operators like var to resolve values.

If $logic is a simple array of multiple statements, apply() will return an array of the results of each statement.

use JWadhams\JsonLogic;

$logic = ['==' => [['var' => 'x'], 10]];
$data = ['x' => 10];

$result = JsonLogic::apply($logic, $data);
// $result is true

The library includes several built-in operators for comparison, math, logic, and data manipulation: