<meta property="og:title" content=""><div id="content"></div>
<?php
$Strings = explode("\n", file_get_contents('strings.txt'));
$String = $Strings[rand(0, count($Strings) - 1)];
?>
....
<meta property="og:title" content="<?= $String ?>">
......
<div id="content"><?= $String ?></div>
.........
<?php
$file = new SplFileObject("file.txt"); // open file
$file->seek(PHP_INT_MAX);
$linecount = $file->key();
$rand = rand(0, $linecount-1); // choose random number
$file->seek($rand); // get random line
?>
<meta property="og:title" content="<? echo $file->current(); ?>">
<div id="content"><? echo $file->current(); ?></div>