prod/php/ElasticOTel/Util/SingletonInstanceTrait.php

<?php

/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/** @noinspection PhpIllegalPsrClassPathInspection */

declare(strict_types=1);

namespace Elastic\OTel\Util;

/**
 * Code in this file is part of implementation internals, and thus it is not covered by the backward compatibility.
 *
 * @internal
 */
trait SingletonInstanceTrait
{
    /**
     * Constructor is hidden because instance() should be used instead
     */
    use HiddenConstructorTrait;

    private static ?self $singletonInstance = null;

    public static function singletonInstance(): self
    {
        if (self::$singletonInstance === null) {
            self::$singletonInstance = new static();
        }
        return self::$singletonInstance;
    }
}