help with log.txt

Hello there, this is the code

<?php

 $iplogfile = "log.txt";
 $fp = fopen($iplogfile, "a");

 if ($fp)
 {
  fputs($fp, $_SERVER["REMOTE_ADDR"]." \n");
  fclose($fp);
 }

?>

PHP:

Can someone help me how i can make if the $_SERVER["REMOTE_ADDR"] is aready on log.txt to dont add again the ip on log.txt

Thanks

 

<?php

 $ip_log_file_name = "log.txt";
 $ip_array = file($ip_log_file_name);
 $fp = fopen($ip_log_file_name, "a");

 if ($fp && !in_array($_SERVER["REMOTE_ADDR"]." \n", $ip_array))
 {
  fputs($fp, $_SERVER["REMOTE_ADDR"]." \n");
  fclose($fp);
 }

?>

PHP:

 

works thanks