Domāju, ka vēlies panākt:
printf("%s", $foo['x']);
...vai:
foreach ($foo as $x) {
printf("%s", $x]);
}
Bet jebkura gadījumā, nevajag jums tos printf, sprintf uc. f'us...:
<?php foreach ($foo as $x): ?>
<span class="content"><?php echo $x['content']; ?></span>
<?php endforeach; ?>