我不能通过fgets（filename）回显文件的内容。

Here is my code. I don't know why I am not getting any thing on page.Suggest me a mode in which if I want to run my code everytime, it should append at the end. and i should also be able to read from it

<?php 

$a=fopen("Welcome.txt","a+");
fwrite($a, "abc");
echo fgets($a);

fclose($a);

?>

You are using the wrong mode for fopen.

$a = fopen("Welcome.txt","r");
var_dump($a);

a+ will "Open for reading and writing" and "If the file does not exist, attempt to create it".

Instead of using fgets use file_get_contents() and file_put_contents() instead of fwrite IMO it's a lot cleaner and easier to understand.