length.php

<?php
  require_once('includes/length.php');

  // Default empty variables
  $fromValue = '';
  $fromUnit = '';
  $toUnit = '';
  $toValue = '';

  /* Check conversion request on submit */
  if ($_POST['submit']) {
    $fromValue = $_POST['fromValue'];
    $fromUnit = $_POST['fromUnit'];
    $toUnit = $_POST['toUnit'];

    $toValue = convertLength($fromValue, $fromUnit, $toUnit);
  }
?>
<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>Convert Length</title>
  <link href="styles.css" rel="stylesheet" type="text/css">
</head>

<body>

  <div id="main-content">

    <h1>Convert Length</h1>

    <form action="" method="post">

      <div class="entry">
        <label>From:</label>&nbsp;
        <input type="text" name="fromValue" value="<?php { echo $fromValue;} ?>" />&nbsp;
        <select name="fromUnit">
          <option value="inches"<?php
            if ($fromUnit == 'inches') {
              {
                echo " selected";
              }
            }
          ?>>inches</option>
          <option value="feet"<?php
            if ($fromUnit == 'feet') {
              {
                echo " selected";
              }
            }
          ?>>feet</option>
          <option value="yards"<?php
            if ($fromUnit == 'yards') {
              {
                echo " selected";
              }
            }
          ?>>yards</option>
          <option value="miles"<?php
            if ($fromUnit == 'miles') {
              {
                echo " selected";
              }
            }
          ?>>miles</option>
          <option value="millimeters"<?php
            if ($fromUnit == 'millimeters') {
              {
                echo " selected";
              }
            }
          ?>>millimeters</option>
          <option value="centimeters"<?php
            if ($fromUnit == 'centimeters') {
              {
                echo " selected";
              }
            }
          ?>>centimeters</option>
          <option value="meters"<?php
            if ($fromUnit == 'meters') {
              {
                echo " selected";
              }
            }
          ?>>meters</option>
          <option value="kilometers"<?php
            if ($fromUnit == 'kilometers') {
              {
                echo " selected";
              }
            }
          ?>>kilometers</option>
        </select>
      </div>

      <div class="entry">
        <label>To:</label>&nbsp;
        <input type="text" name="toValue" value="<?php { echo $toValue;} ?>" />&nbsp;
        <select name="toUnit">
          <option value="inches"<?php
            if ($toUnit == 'inches') {
              {
                echo " selected";
              }
            }
          ?>>inches</option>
          <option value="feet"<?php
            if ($toUnit == 'feet') {
              {
                echo " selected";
              }
            }
          ?>>feet</option>
          <option value="yards"<?php
            if ($toUnit == 'yards') {
              {
                echo " selected";
              }
            }
          ?>>yards</option>
          <option value="miles"<?php
            if ($toUnit == 'miles') {
              {
                echo " selected";
              }
            }
          ?>>miles</option>
          <option value="millimeters"<?php
            if ($toUnit == 'millimeters') {
              {
                echo " selected";
              }
            }
          ?>>millimeters</option>
          <option value="centimeters"<?php
            if ($toUnit == 'centimeters') {
              {
                echo " selected";
              }
            }
          ?>>centimeters</option>
          <option value="meters"<?php
            if ($toUnit == 'meters') {
              {
                echo " selected";
              }
            }
          ?>>meters</option>
          <option value="kilometers"<?php
            if ($toUnit == 'kilometers') {
              {
                echo " selected";
              }
            }
          ?>>kilometers</option>
        </select>

      </div>

      <input type="submit" name="submit" value="Submit" />
    </form>

    <br/>
    <a href="index.php">Return to menu</a>

  </div>
</body>

</html>