php-arrays
processing arrays

From previous notes but not mentioned explicitly: We can shorten silly-page_php.txt to silly-page-v2_php.txt.
(Self-quiz: Why can't pull up silly-page.php and select Developer → View Source, to see the php code?)

Arrays, and looping over them:

         $frontRow = array( "Aaron", "Alvin", Isaac" );
         echo $frontRow[1];

To loop over an array, use foreach:

         $countA = 0;
         foreach ($frontRow as $student) {
           if ($substr($student,0,1)==="A") {
             $countA = $countA + 1;
             }
           }
         echo $countA . " names start with 'A'.";

Don't loop over an array using numeric indices in php: Many times arrays have non-numeric indices . More examples (including using strings-as-indices): See php-ch02-simple.php.

Suppose we want to write a function that takes an array of strings, and returns a string: the HTML for an unordered list.

What is a good name for this function?
What test cases do we consider?

Note that part of your test case is deciding what is the desired amount of whitespace to be included in the answer.

echo "Actual:  ", stringsToUL( array() );
echo "Desired: ", "<ul>
</ul>
";

echo "Actual:  ", stringsToUL( array("Aaron") );
echo "Desired: ", "<ul>
     <li>Aaron</li>
</ul>
";

echo "Actual:  ", stringsToUL( array("Aaron", "Isaac", "Alvin") );
echo "Desired: ", "<ul>
     <li>Aaron</li>
     <li>Isaac</li>
     <li>Alvin</li>
</ul>
";

Once we have this, the code is straightforward:

/* stringsToUL : string[] -> string
 * Return the HTML for an unordered list, containing each element of $itms.
 * (Those strings may themselves contain HTML, so they are NOT SANITIZED HERE.)
 */
function stringsToUL( $itms ) {
  $lineItemsSoFar = "";
  foreach ($itms AS $itm) {
    $lineItemsSoFar .= "    <li>$itm</li>\n";
    }
  return "<ul>\n" . $lineItemsSoFar . "</ul>\n";
  }

In retrospect, the function-name stringsToUL is fine, but the name might be toUL might be equally good.

¹Or, numeric indices that aren't contiguous. ↩

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php-arrays processing arrays

php-arrays
processing arrays