$url = explode(',',I('img'))[1]; //这里的I('img')是base64格式

$img = base64_decode( $url);

$path = "./goodimg/";

$prefix='good_';

$output_file = $prefix.time().rand(100,999).'.jpg';

$path = $path.$output_file;

// 创建将数据流文件写入我们创建的文件内容中

$ifp = fopen( $path, "wb" );

fwrite( $ifp, base64_decode( $url) );

fclose( $ifp );