PHP 标记风格
当解析一个文件时，PHP 会寻找起始和结束标记，也就是 ，这告诉 PHP 开始和停止解析二者之间的代码。此种解析方式使得 PHP 可以被嵌入到各种不同的文档中去，而任何起始和结束标记之外的部分都会被 PHP 解析器忽略。
PHP 也允许使用短标记 和 ?>，但不鼓励使用。只有通过激活 php.ini 中的 short_open_tag 配置指令或者在编译 PHP 时使用了配置选项 --enable-short-tags 时才能使用短标记。
如果文件内容是纯 PHP 代码，最好在文件末尾删除 PHP 结束标记。这可以避免在 PHP 结束标记之后万一意外加入了空格或者换行符，会导致 PHP 开始输出这些空白，而脚本中此时并无输出的意图。
// standard tags- 建议使用
?> // short tags, need short_open_tag enabled in php.ini
// asp tags, need asp_tags enabled in php.ini
// Script
<?php echo "标准标记<p>";?><script language="php"> echo "脚本风格";</script>
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