<"Content-type: text/html; charset=utf-8");
 //write data
 $f = fopen('data','w');//打开文件
 fwrite($f,'Hello PHP');//写入数据
 fclose($f);//关闭文件
 echo 'OK';
 //windows环境暂时不考虑权限问题

<"Content-type: text/html; charset=utf-8");

//read data
$f = fopen('data','r');
$content = fgets($f);
echo $content;
fclose($f);

<"Content-type: text/html; charset=utf-8");
$f = fopen('data','r');
//读取多行数据 while
while(!feof($f)){//feof() 函数检测是否已到达文件末尾
  $content = fgets($f);
  echo $content;
}
fclose($f);

echo file_get_contents('data');