PHP：extract（$ _ POST）然后get_defined_vars（）什么都不返回...为什么？

Question

I have the following PHP script:

<?php 
  function dump_extracted_post() {
    extract($_POST);
    var_dump(get_defined_vars());
  }
  dump_extracted_post();
?>

To this script, I post a form containing some data, and it produces the following (unexpected) result:

Array(0) {
}

Why do I not see the the posted data?

Is there something I've missed in my understanding of extract() or get_defined_vars()? Is there some sort of security setting that might be interfering with extracting from $_POST ?

I am aware of the frowned upon nature of extract, so perhaps it's a security issue, but scanning the php docs doesn't seem to mention any such issue. I want to use this to do some simple templating.

If I change the script to:

<?php 
  function dump_extracted_post() {
    var_dump($_POST);
  }
  dump_extracted_post();
?>

I see the posted data as expected (so yes, I am definately posting data).

Likewise, if I change the script to:

<?php 
  function dump_extracted_post() {
    $a = 'moocows';
    var_dump(get_defined_vars());
  }
  dump_extracted_post();
?>

I see the expected output:

array(1) {
  ["a"]=>
  string(7) "moocows"
}

Answer 1

Your original function works fine for me. I used the following script (named extract.php) for testing:

<form method="post" aciton="extract.php">
  <input type="text" name="foo" />
  <input type="submit" />
</form>
<pre>
<?php
  function dump_extracted_post() {
    extract($_POST);
    var_dump(get_defined_vars());
  }
  dump_extracted_post();
?>
</pre>

Function extract extracts only those key=>value pairs where key is valid identifier not conflicting with existing variables. So probably keys in your $_POST are either not a valid identifiers or are conficting with existing variables.