Reworked the DaemonCommand.

* Accepts options for PID and log file.
* Uses posix_kill whenever available.
* Checks that the daemon actually started or stopped.
* Try to terminate then kill the daemon.
* Uses the logger or output instead of "echo".

Added a ProcessControl interface and implementations.

Closed #908

PHPCI/ProcessControl/PosixProcessControl.php

@@ -0,0 +1,52 @@
+<?php
+/**
+ * PHPCI - Continuous Integration for PHP
+ *
+ * @copyright    Copyright 2015, Block 8 Limited.
+ * @license      https://github.com/Block8/PHPCI/blob/master/LICENSE.md
+ * @link         https://www.phptesting.org/
+ */
+
+namespace PHPCI\ProcessControl;
+
+/**
+ * Control process using the POSIX extension.
+ *
+ * @author Adirelle <adirelle@gmail.com>
+ */
+class PosixProcessControl implements ProcessControlInterface
+{
+    /**
+     *
+     * @param int $pid
+     * @return bool
+     */
+    public function isRunning($pid)
+    {
+        // Signal "0" is not sent to the process, but posix_kill checks the process anyway;
+        return posix_kill($pid, 0);
+    }
+
+    /**
+     * Sends a TERMINATE or KILL signal to the process using posix_kill.
+     *
+     * @param int $pid
+     * @param bool $forcefully Whetehr to send TERMINATE (false) or KILL (true).
+     */
+    public function kill($pid, $forcefully = false)
+    {
+        posix_kill($pid, $forcefully ? 9 : 15);
+    }
+
+    /**
+     * Check whether this posix_kill is available.
+     *
+     * @return bool
+     *
+     * @internal
+     */
+    public static function isAvailable()
+    {
+        return function_exists('posix_kill');
+    }
+}