4-1验证码类封装之GD库验证

<?php
/**
 * GDBasic.php
 
 * description GD基础类
 */

namespace ImoocLib;


class GDBasic
{
    protected static $_check =false;

    //检查服务器环境中gd库
    public static function check()
    {
        //当静态变量不为false
        if(static::$_check)
        {
            return true;
        }

        //检查gd库是否加载
        if(!function_exists("gd_info"))
        {
            throw new Exception('GD is not exists');
        }

        //检查gd库版本
        $version = '';
        $info = gd_info();
        if(preg_match("/\d+\.\d+(?:\.\d+)?/", $info["GD Version"], $matches))
        {
            $version = $matches[0];
        }

        //当gd库版本小于2.0.1
        if(!version_compare($version,'2.0.1','>='))
        {
            throw new Exception("GD requires GD version '2.0.1' or greater, you have " . $version);
        }

        self::$_check = true;
        return self::$_check;
    }
}