in my case , i need to return value from a ajax page. as i know , there is two way to do it: echo , return.
echo 0;
exit;
or
return 0;
exit;
is there any different between them?
AJAX retrieves the output from another page. echo will output something, but return is for returning a value from a function.
Use echo.
If I were you, I would use :
echo '0';
exit();
Why ? Because you don't want to output an integer (treated as bool in PHP, I assume 0/1). You want a string so AJAX can read it.
Return is for function and stuff, not to end a page.