lect03c
processing input; array functions

We've been talking about input forms (html elements), and then php scripts to process a submitted form:

The URL that handles the submitted form is the one given in the form tag as the submit attribute:

  <!-- inside form.php (or, form.html) -->
  <form submit='submit.php' action="post">
    Login: <input type='text' name='userid' />
    <br />
    Remember me?: <input type='checkbox' name='remember' value='yep' />
    …
  </form>

Use the $_POST (or, $_GET) array to look up values; for indicies (keys), use the name attribute that you gave the input-element back in the html.

  <!-- inside submit.php -->
  <?php
     echo "Hey there ", $_POST['userid'];
     if (array_has_index('remember',$_POST)) {
       echo "How could I ever forget?";
        // $_POST['remember'] = 'yep'
       }
  ?>

Note that checkboxes which weren't checked, etc., don't have any entries in $_POST (even though you might which it had an entry with value “false” or something).
If you gave several input-elements the same name attribute ending in “[]”, then in $_POST look it up without the “[]”, and you'll get an array of all the values (with numeric inidices/keys).

When creating a page which includes something typed in by the user (from a previous text-input), we must be careful! What could the user have typed, that would goof up our web page?

htmlspecialchars
nl2br
(To be discussed in a future lecture, not today:) Note that to prevent errors, some php servers used to enable “magic quotes”: When setting up the $_POST array, they will guard against malicious/accidental breaches by adding a slash in front of any quote-characters.

This has been deprecated and will be discontinued (though php.radford.edu still uses them as of 2011.Sep.16). A poor solution is to always call stripslashes on all input; a better solution is to check whether the server is configured to auto-add slashes, only calling stripslashes when get-magic-quotes-gpc returns true.
stripslashes

Quick q: suppose a user types:

  hi
<3

in a textarea whose name is msg. What is

$_POST['msg']
nl2br($_POST['msg'])
htmlspecialchars($_POST['msg'])
nl2br(htmlspecialchars($_POST['msg']))
htmlspecialchars(nl2br($_POST['msg']))

We have seen arrays, and mentioned that if they have all-numeric indices (keys) then we can process them with a for loop or a while loop, using the same syntax that Java and Javasript happen to use.

Then we saw that if an array has keys which aren't all numeric, we can use a foreach loop to process them:

  $myData = array( 'hi' => 'hallo', 'good day' => 'guten Tag', 'see you later' => 'auf wiedersehen' );

  foreach ($mydata as $german) {
    echo $german, "\n";
    }

  foreach ($mydata as $english => $german) {
    echo "You say '$english', I say '$german'.\n";
    }

The foreach loop is of course one way to process each element of the $_POST array (if you didn't want code specific/different for each input form).

Exercise: Let's write a function which takes in the name of a directory, and returns a string mentioning each file in the directory: something like:

"One file is someFile.txt.<br />Another file is someFile2.txt.<br />Another file is Zzzz.php.<br />"

Hint ¹: scandir.

Exercise: Write a function that takes in an array of key/values pairs, and returning a string that happens to be html for a pull-down menu of those values.

test( HTMLPulldown( array( "Jan" => "January", "Dec" => "December" ) ),
      "<select
  <option value='Jan'>January</option>
  <option value='Dec'>December</option>
</select>" );


test( HTMLPulldown( array( "January", "February", "December" ) ),
      "<select
  <option value='0'>January</option>
  <option value='1'>February</option>
  <option value='2'>December</option>
</select>" );

This is pretty cool. However, looking closely at the generated HTML, there is one thing missing: we want our select node to include a name attribute. What do we need to tweak?

Optional: extend the above by including an optional parameter: a top-option like “please select:”.

Left as an exercise: Similar to above, make a function that takes in an array, and returns (the html for) a bunch of checkboxes, inside table.

¹Usually, a google search like “php list files” gives good matches; in this particular case we get sidetracked by related functions that deal with file-handles and are iterators. ↩

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©2011, Ian Barland, Radford University
Last modified 2011.Sep.19 (Mon) Please mail any suggestions
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lect03c processing input; array functions

lect03c
processing input; array functions