如何从字符串中删除PHP代码？

$string = 'This is some PHP code <?php echo "Hello World"; ?> that needs to be removed.';
$pattern = '/<\?php.*?\?>/s';
$cleanString = preg_replace($pattern, '', $string);
echo $cleanString;

$string = 'This is some PHP code <?php echo "Hello World"; ?> that needs to be removed.';
$start = strpos($string, '<?php');
$end = strpos($string, '?>', $start) + 2;
$cleanString = substr($string, 0, $start) . substr($string, $end);
echo $cleanString;

$string = 'This is some PHP code <?php echo "Hello World"; ?> that needs to be removed.';
$cleanString = '';
ob_start();
eval('?>' . $string . '<?php ');
$cleanString = ob_get_clean();
echo $cleanString;