<?php
$file = 'txt.txt';
$find = '127.0.0.3';
$contents = file_get_contents($file);
$pattern = preg_quote($find, '/');
$pattern = "/^.*$pattern.*$/m";
if(preg_match_all($pattern, $contents, $matches)){
echo "Sonuç bulundu";
//echo implode("n", $matches[0]);
}
else{
echo "Sonuç bulunamadı";
} ?>

127.0.0.1
127.0.0.2
127.0.0.3