打开a.txt文件在文件中最前面加上hello

$dir = "./a.txt";

$handle = fopen($dir,'r');

$read = fread($handle,filesize($dir));

$content = 'hello'.$read;

fclose($handle);

$handle =fopen($dir,'w');

fwrite($handle,$content);

fclose($handle);

file_get_contents($dir);

file_put_contents($dir);