从 PHP 中的变量返回第一句话

我已经找到了类似的线程：

$sentence = preg_replace('/(.*?[?!.](?=\s|$)).*/', '\\1', $string);

但这似乎在我的函数中不起作用：

<?function first_sentence($content) {
    $content = html_entity_decode(strip_tags($content));   
    $content = preg_replace('/(.*?[?!.](?=\s|$)).*/', '\\1', $content);
    return $content;


}?>

当句子作为段落的结尾结束时，似乎没有考虑第一句。有任何想法吗？

/**
 * Get the first sentence of a string.
 *
 * If no ending punctuation is found then $text will
 * be returned as the sentence. If $strict is set
 * to TRUE then FALSE will be returned instead.
 *
 * @param  string  $text   Text
 * @param  boolean $strict Sentences *must* end with one of the $end characters
 * @param  string  $end    Ending punctuation
 * @return string|bool     Sentence or FALSE if none was found
 */
function firstSentence($text, $strict = false, $end = '.?!') {
    preg_match("/^[^{$end}]+[{$end}]/", $text, $result);
    if (empty($result)) {
        return ($strict ? false : $text);
    }
    return $result[0];
}

// Returns "This is a sentence."
$one = firstSentence('This is a sentence. And another sentence.');

// Returns "This is a sentence"
$two = firstSentence('This is a sentence');

// Returns FALSE
$three = firstSentence('This is a sentence', true);