title: Display results on combobox by selecting a value on another combobox
body: <p>I have a problem in my project. I have these categories:</p>
  
  <pre><code>Football
  Basketball
  Tennis
  </code></pre>
  
  <p>and these sub categories:</p>
  
  <pre><code>super league A
  super league B
  euroleague
  Serie A
  </code></pre>
  
  <p>I have the categories and sub categories in my phpMyAdmin DB.
  I have this code now, that I display these two, in two different comboboxes, via queries from DB:</p>
  
  <pre><code>&lt;?php
  $category = mysql_query("SELECT * FROM katigories ORDER BY id_katigoria");
  echo "&lt;select name='katigoria'&gt;";
  echo "&lt;option selected='selected' value='0'&gt; Επιλογή κατηγορίας! &lt;/option&gt;";
  while($values = mysql_fetch_assoc($category))
  {
      echo "&lt;option value='$values[id_katigoria]'&gt;".$values['katigoria']."&lt;/option&gt;";
  }
  echo "&lt;/select&gt;";
  ?&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>&lt;?php
  $category = mysql_query("SELECT * FROM upokatigories ORDER BY id_upokatigoria");
  echo "&lt;select name='upokatigoria'&gt;";
  echo "&lt;option selected='selected' value='0'&gt; Επιλογή υποκατηγορίας! &lt;/option&gt;";
  while($values = mysql_fetch_assoc($category))
  {
      echo "&lt;option value='$values[id_upokatigoria]'&gt;".$values['katigoria']."&lt;/option&gt;";
  }
  echo "&lt;/select&gt;";
  ?&gt;
  </code></pre>
  
  <p>so far so good. But now my problem is that I want to select from the first one Basketball, and I want to see ONLY the euroleague to the second combobox.</p>
  
  <p>I don't know much about JS or jQuery, but I believe between two of them is the answer I am looking for. Am I right?</p>
  
  <p>Please any ideas, to continue, or any suggestions, about what to read and where to look?</p>
  
  <p>P.S. I found something similar here, but it was for C# or/and python..so, I hope I am not repeating any other questions</p>