diff --git a/examples/02-decide-action.php b/examples/02-decide-action.php
new file mode 100644
index 0000000..cd32b45
--- /dev/null
+++ b/examples/02-decide-action.php
@@ -0,0 +1,55 @@
+<?php
+
+use \Parallel\Prefork;
+
+require_once __DIR__ . '/../vendor/autoload.php';
+
+main();
+exit();
+
+function main()
+{
+    $start_time = time();
+    $prev_workers = 5;
+    $pp = new Prefork(array(
+        'max_workers'  => 5,
+        'trap_signals' => array(
+            SIGHUP  => SIGTERM,
+            SIGTERM => SIGTERM,
+        ),
+        'decide_action' => function($current_worker, $max_worker) use($start_time, &$prev_workers) {
+            $current_time = time();
+            $max_worker = $max_worker + (int)(($current_time - $start_time) / 6);
+            if ( $max_worker > 10 ) {
+                $max_worker = 10;
+            }
+            if ( $max_worker !== $prev_workers ) {
+                echo "===> max worker: $prev_workers => $max_worker\n";
+                $prev_workers = $max_worker;
+            }
+            return $current_worker < $max_worker;
+        },
+    ));
+    while ($pp->signalReceived() !== SIGTERM) {
+        loadConfig();
+        if ($pp->start()) {
+            continue;
+        }
+        workChildren();
+        $pp->finish();
+    }
+    $pp->waitAllChildren();
+}
+
+function loadConfig()
+{
+    echo "Load configuration\n";
+}
+
+function workChildren()
+{
+    for ($i = 1; $i <= 3; $i++) {
+        echo "Sleep $i seconds\n";
+        sleep($i);
+    }
+}
diff --git a/lib/Prefork.php b/lib/Prefork.php
index 3f99fcf..2b61ddd 100644
--- a/lib/Prefork.php
+++ b/lib/Prefork.php
@@ -27,10 +27,15 @@ class Prefork
     public $err_respawn_interval = 1;
 
     /**
-     * @var callable lamda function that is called when a child is reaped
+     * @var callable lambda function that is called when a child is reaped
      */
     public $on_child_reap = null;
 
+    /**
+     * callable lambda fuction that decide action
+     */
+    private $decide_action = null;
+
     private $signal_received = null;
     private $manager_pid     = null;
     private $in_child        = false;
@@ -43,6 +48,11 @@ function __construct(array $args = array())
             ? $args['max_workers'] : $this->max_workers;
         $this->trap_signals = isset($args['trap_signals'])
             ? $args['trap_signals'] : $this->trap_signals;
+        $this->decide_action = isset($args['decide_action'])
+            ? $args['decide_action'] : null;
+        if ( isset($this->decide_action) && !is_callable($this->decide_action) ){
+            die("decide_action should be callable\n");
+        }
 
         foreach (array_keys($this->trap_signals) as $sig) {
             pcntl_signal($sig, array($this, '_signalHandler'), false);
@@ -75,7 +85,16 @@ public function start()
         // main loop
         while ($this->signal_received === null) {
             $pid = null;
-            if (count(array_keys($this->worker_pids)) < $this->max_workers) {
+            $currect_workers = count(array_keys($this->worker_pids));
+            $should_fork = $currect_workers < $this->max_workers;
+            if ( is_callable($this->decide_action) ) {
+                try {
+                    $should_fork = call_user_func_array($this->decide_action,array($currect_workers, $this->max_workers));
+                } catch ( \Exception $e ) {
+                    printf("Exception. Use default action: %s\n",$e->getMessage());
+                }
+            }
+            if ($should_fork) {
                 $pid = pcntl_fork();
                 if ($pid === -1) {
                     echo "fork failed!\n";
@@ -164,16 +183,16 @@ private function generation()
         return $this->generation;
     }
 
-    // PHP 5.2.x don't have lamda function
     private function _runChildReapCb($exit_pid, $status)
     {
         $cb = $this->on_child_reap;
-        if ($cb) {
-/*
+        if (is_callable($cb)) {
             try {
-                $cb->($exit_pid, $status);
-            }
-*/
+                call_user_func_array($cb, array($exit_pid, $status));
+            } catch (\Exception $e) {
+                // ignore
+                printf("Ignore Exception: %s\n",$e->getMessage());
+            };
         }
     }
 }