php - 如何识别php中的字符串？

Question

当我输入：

<?php
  $temp="1234";
  echo "<script type='text/javascript'>document.write({$temp});</script>";
?>

我在屏幕上得到 1234。

但是当我替换$temp="1234"为时$temp="alfa"，屏幕上什么也没有。

有什么问题 ？我哪里错了？“1234”和“alfa”都是字符串

Answer 1

alert(1234) is valid javascript, and will simply pop up the integer 1234 on your screen. alert(alfa) is attempting to pop up the contents of a variable named alfa on your screen, which doesn't exist.

If you're insert data from PHP into a Javascript context, you MUST use json_encode() to ensure that you're producing VALID javascript. e.g.

$temp = 'alfa';
$json=  json_encode($temp);
echo '<script>.... {$json}...</script>';

that will produce alert('alfa') and work as expected.

Answer 2

您没有将文本括在表示字符串的双引号字符 '"' 中。

document.write(1234)之所以有效，是因为1234它是 JavaScript 中的有效值（整数），而alfa它是符号名称，它应该是"alfa".