There are a couple of usage patterns to choose from.

Simple checks

For simple checks use static function checkValue()

if (Cheque::checkValue($value, $query)) {}

Reusing the query

When you want to reuse your query, or pass it somewhere as a callback, create the object and call check method, or invoke the object.

// build the query object
$chequer = new Chequer($query);

// use it witch check()
if ($chequer->check($value)) {}

// or invoke it as a function
if ($chequer($value)) {}

// or pass it as a callback
array_filter($array, $chequer);

Global configuration

You can store all your queries in configuration files and use them when they are needed. This way you can separate your validation/filtering logic from your code - just like you do with the templates!

// load the rules from the JSON file
Chequer::addGlobalRules(json_decode(file_get_contents('queries.json'), JSON_OBJECT_AS_ARRAY));

// reuse them
if (Chequer::checkValue($value, ['$rule' => 'some_defined_rule'])) {}

As every query is a scalar or an array - they can be easely stored in JSON, YAML, MongoDB - you name it.

Dependency injection

If you rather prefer DI - fret not. You can add rules to Chequer objects directly, which means you can make a factory, or pass the Chequer object around and still populate it with predefined rules.

The above example rewritten as Silex factory:

// load the queries once
$app['chequer.rules'] = $app->share(function() {
        return json_decode(file_get_contents('queries.json'), JSON_OBJECT_AS_ARRAY);
// always have a fresh chequer on hand
$app['chequer'] = function() use ($app) { 
    return (new Chequer())->addRules($app['chequer.rules']);

// reuse
if ($app['chequer']->query($value, ['$rule' => 'some_defined_rule'])) {}


In case you want to add your own built-in operators, or typecasts you can extend the Chequer class and define protected function with the name operator* and typecast*.

To define the $true operator:

protected function operator_true($value, $rule) {
    return $rule == true;

Or you can add the operator/alias to the $operators protected parameter.


Array filtering

This will leave only values from 2 to 5 in the array.

$array = [1, 2, 3, 4, 5, 6];
$array = array_filter($array, new Chequer(['$between' => [2, 5]]))

Iterator filtering

This will iterate through files with 'php' or 'html' extensions, that are older than one day.

$files = new FilesystemIterator(dirname(__DIR__));
$files = new CallbackFilterIterator($files, 
             new Chequer('$ @file() => (.extension $in(php, html) && (.mtime < -1 day))')
foreach($files as $file) {}

Data querying

You can even read and translate the data... This will ouput information about biggest countries with the highest GDP, and transpose it to another format:

// data for 10 most populated countries on earth
$populatedCountries = '[{"gdp":7973000,"name":"China","pop":1330044000},{"gdp":3297000,"name":"India","pop":1173108018},{"gdp":14260000,"name":"United States","pop":310232863},{"gdp":914600,"name":"Indonesia","pop":242968342},{"gdp":1993000,"name":"Brazil","pop":201103330},{"gdp":427300,"name":"Pakistan","pop":184404791},{"gdp":224000,"name":"Bangladesh","pop":156118464},{"gdp":335400,"name":"Nigeria","pop":154000000},{"gdp":2266000,"name":"Russia","pop":140702000},{"gdp":4329000,"name":"Japan","pop":127288000}]';
$populatedCountries = json_decode($populatedCountries, JSON_OBJECT_AS_ARRAY);

echo implode("\n", 
    // If gdp is more then 5mln return "#### with #### of GDP". Otherwise return NULL which is filtered out.    
    Chequer::shorthand('(.gdp > 5000000) ? (.name with .gdp of GDP) : NULL')
/* This will output:
   China with 7973000 of GDP
   United States with 14260000 of GDP

$newFormat = json_encode( 
    // If gdp is more then 5mln add {### : {gdp : ###, pop : ###}} to the results
    Chequer::shorthand('(.gdp > 5000000) ? (.name : (gdp:.gdp, pop:.pop)) : NULL')
/** New format will be:
    {"China":{"gdp":7973000,"pop":1330044000},"United States":{"gdp":14260000,"pop":310232863}}

Environment variables checking

This example will match all users from localhost, plus those with IP starting from '192' and having a 'debug' cookie.

Btw., the checkEnvironment function is a neat shortcut for checking _SERVER, _ENV, _COOKIES etc. in one go.

if (Chequer::checkEnvironment([
    ['REMOTE_ADDR' => ['', 'localhost']],
    ['REMOTE_ADDR' => ['$regex' => '/^192\./'], '_COOKIE' => ['debug' => true]]
], false)) {
    echo 'Debug!';

Command line input

Shorthand syntax may come in handy in console applications.

Ductape - a PHP Build tool - accepts Chequer everywhere there is something to filter. For example this command will list all the files, including subdirectories, whose size is more than 1MB and they are not archives.

ductape.phar files --filter "$ @file().size > 1000000 && ! (@file().ext $in (zip,rar,tar,tgz))" .