Add progress callback

examples/progress.php

@@ -0,0 +1,31 @@
+<?php
+require '../src/Curl/Curl.php';
+
+use \Curl\Curl;
+
+$last_progress = 0;
+$last_progress_time = 0;
+
+$curl = new Curl();
+$curl->progress(function ($client, $download_size, $downloaded, $upload_size, $uploaded){
+
+    global $last_progress;
+    global $last_progress_time;
+
+    if($download_size == 0)
+        return;
+
+    $now = time();
+
+    $progress = floor( $downloaded * 100 / $download_size );
+
+    // print progress every one second
+    if(($now - $last_progress_time) > 1 && $last_progress != $progress)
+    {
+        echo $progress . "%\n";
+
+        $last_progress      = $progress;
+        $last_progress_time = $now;
+    }
+});
+$curl->download('http://php.net/distributions/manual/php_manual_en.html.gz', '/tmp/php_manual_en.html.gz');