log-driver.php: split up log driver

inc/Data/Driver/StderrLogDriver.php

@@ -0,0 +1,27 @@
+<?php
+namespace Vichan\Data\Driver;
+
+defined('TINYBOARD') or exit;
+
+
+/**
+ * Log to php's standard error file stream.
+ */
+class StderrLogDriver implements LogDriver {
+	use LogTrait;
+
+	private string $name;
+	private int $level;
+
+	public function __construct(string $name, int $level) {
+		$this->name = $name;
+		$this->level = $level;
+	}
+
+	public function log(int $level, string $message): void {
+		if ($level <= $this->level) {
+			$lv = $this->levelToString($level);
+			\fwrite(\STDERR, "{$this->name} $lv: $message\n");
+		}
+	}
+}