vasiaduman

$file = 'file.txt';

$file_strings_arr = file($file);
$strings_amount   = sizeof($file_strings_arr);
$string_for_del   = rand(0, $strings_amount - 1);

print $file_strings_arr[$string_for_del];

unset($file_strings_arr[$string_for_del]);
file_put_contents($file, implode('', $file_strings_arr));