WordPress在一定字数之后添加自定义内容

add_filter('the_content', 'zm_insert_content_after_chars_words');
function zm_insert_content_after_chars_words($content) {
	// 当超过1000个字符时执行此操作
	$enable_length = 1500;
	// 在500个字符后的第一个</p>之后插入
	$after_character = 1500;
	if ( is_single() && strlen( $content ) > $enable_length ) {
		$before_content = substr( $content, 0, $after_character );
		$after_content = substr($content, $after_character );
		$after_content = explode( '</p>', $after_content );
		$text = '文字内容';
		array_splice( $after_content, 1, 0, $text );
		$after_content = implode( '</p>', $after_content );
		return $before_content . $after_content;
	} else {
		return $content;
	}
}