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vendor/yiisoft/yii2/base/StaticInstanceTrait.php

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+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\base;
+
+use Yii;
+
+/**
+ * StaticInstanceTrait provides methods to satisfy [[StaticInstanceInterface]] interface.
+ *
+ * @see StaticInstanceInterface
+ *
+ * @author Paul Klimov <klimov.paul@gmail.com>
+ * @since 2.0.13
+ */
+trait StaticInstanceTrait
+{
+    /**
+     * @var static[] static instances in format: `[className => object]`
+     */
+    private static $_instances = [];
+
+
+    /**
+     * Returns static class instance, which can be used to obtain meta information.
+     * @param bool $refresh whether to re-create static instance even, if it is already cached.
+     * @return static class instance.
+     */
+    public static function instance($refresh = false)
+    {
+        $className = get_called_class();
+        if ($refresh || !isset(self::$_instances[$className])) {
+            self::$_instances[$className] = Yii::createObject($className);
+        }
+        return self::$_instances[$className];
+    }
+}