“为什么”脚本不打印任何内容？ [英] 'Why' doesn't the script print anything?

问题描述

当我运行以下脚本时，什么都不会打印。为什么会这样呢？

When I run the following script, nothing gets printed. Why is it so ?

<?php
  $var = "<?php echo 'Hey !'; ?>";
  echo $var;
?>

推荐答案

它回显无，因为您的浏览器没有了解<？php 标签，因此不会显示标签内容；

It echoes "nothing" because your browser doesn't understand <?php tags, so it won't show the tag contents; it should show something when you select view the page source though.

此行为的原因是脚本的默认内容类型设置为 text / html （您可以通过查看响应标题来确认），并且在HTML上下文中，应使用 htmlspecialchars（）

The reason for this behaviour is that the default content type of your script is set as text/html (you can confirm this by looking at the response headers) and in the context of HTML, you should use htmlspecialchars()

echo htmlspecialchars($var);

实际上，作为一般规则，在输出变量时应始终对其进行适当的转义。

In fact, as a general rule, you should always escape variables appropriately when you output them.

或者，您可以让浏览器知道您的输出不应被解释为HTML；您可以通过设置适当的响应标题来做到这一点：

Alternatively you could let the browser know that your output should not be interpreted as HTML; you can do this by setting an appropriate response header:

header('Content-Type: text/plain');

使用上述内容类型，浏览器会逐字显示输出。

With the above content type your output is shown verbatim by the browser.

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