PHP closure usage example

A_closure_example.php

<?php

$myReport = new MyReport;
$myReport->report();

// 2019-08-08: MyReport started
// 2019-08-08: using logReport
// 2019-08-08: Reporting: First report
// 2019-08-08: Reporting: Second report

Log.php

<?php

/**
 * Does the actual logging.
 */
class Log
{
    /**
     * Writes a message to the log.
     *
     * @param string $msg
     */
    function add(string $msg)
    {
        $now = date('Y-m-d');
        error_log("$now: $msg");
    }
}

MyReport.php

<?php

/**
 * Creates a report using the Reporter class.
 *
 * Defines that logging should be done using the Log object.
 * Passes a logger closure to the Reporter object.
 * Reporter doesn't know or care about the type of the logger object.
 */
class MyReport
{
    /** @var Log Logger object */
    private $log;

    function __construct()
    {
        /** @var Log log */
        $this->log = new Log;
        $this->log->add('MyReport started');
    }

    /**
     * Creates a report.
     */
    function report()
    {
        /**
         * Wraps logging a message.
         *
         * @param string $message
         */
        $logReport = function (string $message) {
            $this->log->add($message);
        };

        $logReport('using logReport');

        $reporter = new Reporter($logReport);
        $reporter->report('First report');
        $reporter->report('Second report');
    }
}

Reporter.php

<?php

/**
 * Reports on stuff (TBD).
 *
 * Logs reported stuff using given logger closure.
 * Does not know anything about the used logging class.
 */
class Reporter
{
    /** @var Closure Function that does the logging */
    private $loggerFunc;

    /**
     * Reporter constructor.
     *
     * @param Closure $logger Logging function (message: string): void
     */
    function __construct(Closure $logger)
    {
        $this->loggerFunc = $logger;
    }

    /**
     * Reports on stuff.
     *
     * @param string $msg Message to report
     */
    function report(string $msg)
    {
        $log = $this->loggerFunc;
        $log("Reporting: $msg");

        // do actual reporting
    }
}