Delete line no match with current date server with PHP

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PHP

Hello everyone!
Content of the text file (test.txt):

115.5.108.249 2015-03-01
118.110.6.87 2018-01-03
36.120.105.13 2018-04-06

I'm familiar with the following:

<?php 
    $fname = "test.txt";
    $date = date("Y-m-d");
    foreach($lines as $line) if(!strstr($line, $date)) $out .= $line;  
    $f = fopen($fname, "w");  
    fwrite($f, $out);  
    fclose($f);
?> 

This command will only delete the line that contains the current server history and date ($date). I want this command to run in reverse. Line cleaner whose history (date) is old and no match with current server date (The server where PHP runs). I hope you understand what I mean.
Thanks.

What I have tried:

<?php
$fname = "test.txt";
$date = date("Y-m-d");
foreach($lines as $line) if(!strstr($line, $date)) $out .= $line;
$f = fopen($fname, "w");
fwrite($f, $out);
fclose($f);
?>