求解这四句代码的作用讲解?
$html = preg_replace('/>(\s+)/','>',$html);
$html = preg_replace('/(\s+)</','<',$html);
$html = str_replace("\r\n",'',$html);
$html = str_replace("\t",'',$html);
$html = preg_replace('/>(\s+)/','>',$html);
$html = preg_replace('/(\s+)</','<',$html);
$html = str_replace("\r\n",'',$html);
$html = str_replace("\t",'',$html);
第三句替换回车为空
第四句替换制表符(tab)为空
$html = preg_replace('/(\s+)</','<',$html);// 用‘<’替换 ‘<’和空白部分!
$html = str_replace("\r\n",'',$html); // 去掉换行和回车,
$html = str_replace("\t",'',$html); // 去掉 制表符