ITEC 325 2013spring ibarland

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lect04a
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 indices (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 wish it had an entry with value “false” or something).
• If you gave several input-elements the same name attribute, and the name ends 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

• 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 default-server-behavior has been deprecated and may be discontinued eventually (though php.radford.edu still uses them as of 2012.Feb.10).

  A poor solution is to always call stripslashes on all input. A better solution — one that won't have to change if the server's behavior changes — is to check whether or not the server is configured to auto-add slashes, via get_magic_quotes_gpc, and only call stripslashes in that case.

  /** Return the input from a user form. * @Return the input from a user form, */ function getInput($name) { $formInput = trim( $_POST[$name] ); return get_magic_quotes_gpc() ? stripslashes($formInput) : $formInput ); }

Quick q: suppose a user types:

  hi
<3

• $_POST['msg']
• nl2br($_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";
    }

File timestameps (and, directory-processing)

When looking at files, it can be nice to include their most recently

Before calling filemtime (which takes in a file-name, and returns a date):

  ; Either:
  ini_set('date.timezone','America/New_York');
  date_default_timezone_set('America/New_York');

  echo strtotime('2012-Feb-08 11:03:27');   // don't use '2012.Feb.08 ...'; it returns null.
  echo date('Y-M-d H:m:s',234234234);

Look at the documentation for scandir.
Since it returns an array of filenames, it's a natural match to use with other functions that want an array of strings: For example, echo htmlLines( scandir( '/ibarland/Tmp' ) );

array_map

Recall from hw03: we wanted an English list of hyperlinks, separated by commas, with the word "and" before the last item. And you just wrote a function for making an English list, and you called that. The array you pass in must be an array of URLs.

To create the array, hopefully you also used your function hyperlink, written from hw02. (If you wrote the same long HTML a tag over and over, that's a sign that a function would be better.) So you might have a loop:

  $URLsAsText = array( "http://d20srd.org", "http://www.radford.edu", "http://google.com" );

  $URLsAsHTML = array();
  foreach ($URLsAsText AS $url) {
     $URLsAsHTML[] = hyperlink($url);
     }

  echo "It should appeal to ", commaSeparatedList( $URLsAsHTML ), "."
  

Any other repeated stuff? Hmm, the “http:” prefix was kinda annoying, but writing a loop for that seems definite overkill.
(Design Question: Should hyperlink prepend a http:?)

It's kinda annoying to keep writing loops that make a new array of updated values. Most of the loop is very rote — the only part that differs is the particular rule to transform the individual element to the new element. (In the example above, the answer is “the function hyperlink”.)

There is a handy function, array_map: You pass it an array of data, and you pass it the rule (function) on how to transform each individual datum, and it gives you back the entire transformed array. So our loop above gets turned in to:

  $URLsAsText = array( "http://d20srd.org", "http://www.radford.edu", "http://google.com" );
  $URLsAsHTML = array_map( $URLsAsText, "hyperlink" );
  echo "It should appeal to ", commaSeparatedList( $URLsAsHTML ), ".";

  $URLsAsText = array( "http://d20srd.org", "http://www.radford.edu", "http://google.com" );
  echo "It should appeal to ", 
       commaSeparatedList( array_map( $URLsAsText, "hyperlink" ) ),
       ".";

Finally, note that we can also handle the “prepend “http://” to each item” issue. We could make a separate function and apss that to array_map, or we could use an anonymous function:

  $URLsAsText = array_map( array( "d20srd.org", "www.radford.edu", "google.com" ),
                           function ($domain) { return "http://" . $domain; } );

  echo "It should appeal to ", 
       commaSeparatedList( array_map( array( "http://d20srd.org",
                                             "http://www.radford.edu",
                                             "http://google.com" ),
                                      "hyperlink" ) ),
       ".";

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©2012, Ian Barland, Radford University Last modified 2013.Feb.22 (Fri)

Please mail any suggestions (incl. typos, broken links) to ibarlandradford.edu