improve code for php 5.5

lib/DirScanner.php

@@ -51,17 +51,17 @@ Class DirScanner {
         'm3u8',    //视频
     );
     protected $maxReadFilesize = array(                  //默认每种文件读取内容最大大小
-        'txt' => 100*1024,          //纯文本
-        'md' => 5*1024*1024,        //纯文本
-        'url' => 20*1024,           //快捷方式
-        'jpg' => 500*1024,          //图片
-        'jpeg' => 500*1024,         //图片
-        'png' => 500*1024,          //图片
-        'gif' => 500*1024,          //图片
-        'ico' => 50*1024,           //图标
-        'mp4' => 100*1024*1024,     //视频
-        'ts' => 10*1024*1024,       //视频
-        'm3u8' => 10*1024*1024,     //视频
+        'txt' => 102400,          //纯文本
+        'md' => 5242880,        //纯文本
+        'url' => 20480,           //快捷方式
+        'jpg' => 512000,          //图片
+        'jpeg' => 512000,         //图片
+        'png' => 512000,          //图片
+        'gif' => 512000,          //图片
+        'ico' => 51200,           //图标
+        'mp4' => 104857600,     //视频
+        'ts' => 10485760,       //视频
+        'm3u8' => 10485760,     //视频
     );
     protected $securedFileExtensions = array(            //开启Nginx防盗链的文件类型
         'jpg',     //图片

php_extension_install.md

@@ -0,0 +1,12 @@
+# PHP Extensions needed
+
+* php-mbstring
+
+
+## install php extensions in docker
+
+```
+docker exec -it {container id} sh
+apk add php-mbstring
+...
+```