silverstripe-framework/src/Core/DatabaselessKernel.php

<?php

namespace SilverStripe\Core;

use Exception;

/**
 * Boot a kernel without requiring a database connection.
 * This is a workaround for the lack of composition in the boot stages
 * of CoreKernel, as well as for the framework's misguided assumptions
 * around the availability of a database for every execution path.
 *
 * @internal
 */
class DatabaselessKernel extends BaseKernel
{
    /**
     * Indicates whether the Kernel has been flushed on boot
     * Uninitialised before boot
     *
     * @var bool
     */
    private $flush;

    /**
     * Allows disabling of the configured error handling.
     * This can be useful to ensure the execution context (e.g. composer)
     * can consistently use its own error handling.
     *
     * @var boolean
     */
    protected $bootErrorHandling = true;

    public function setBootErrorHandling(bool $bool)
    {
        $this->bootErrorHandling = $bool;
        return $this;
    }

    /**
     * @param false $flush
     * @throws Exception
     */
    public function boot($flush = false)
    {
        $this->flush = $flush;

        $this->bootPHP();
        $this->bootManifests($flush);
        $this->bootErrorHandling();
        $this->bootConfigs();

        $this->setBooted(true);
    }

    /**
     * @return bool
     */
    public function isFlushed()
    {
        return $this->flush;
    }
}