如何创建语义搜索

I want to create a search box where instead of using a WHERE cluse in the query to match the exact phrase within a field, I want the search box to be able to perform a semantic search so that when the user enters in part of a phrase, it displays suitable results where it is able to match the meaning of a phrase. Exactly how Google works when you try and search through Google. Is this possible to achieve and does anyone have any ideas?

Below is the code I am currently using to be able to use the database to see if a row matches the exact phrase entered within the search box:

  <?php


    //connected to DB

          foreach (array('questioncontent') as $varname) {
            $questioncontent = (isset($_POST[$varname])) ? $_POST[$varname] : '';
          }

    ?>


    <p>Search for a previous question by entering in a phrase in the search box below and submitting the phrase</p>

    <form action="previousquestions.php" method="post" id="modalform">
          <p>Search: <input type="text" name="questioncontent" value="<?php echo $questioncontent; ?>" /></p>
          <p><input id="searchquestion" name="searchQuestion" type="submit" value="Search" /></p>
          </form>


    <?php 
                if (isset($_POST['searchQuestion'])) {

                  $questionquery = "SELECT QuestionContent FROM Question
              WHERE(QuestionContent = '".mysql_real_escape_string($questioncontent)."')";

          $questionnum = mysql_num_rows($questionresult = mysql_query($questionquery));

          if($questionnum !=0){

          $output = "";

            while ($questionrow = mysql_fetch_array($questionresult)) {

    $output .= "
          <table>
          <tr>
          <td>{$questionrow['QuestionContent']}</td>
          </tr>";
            }
            $output .= "        </table>";

            echo $output;

      }

    }

If you are looking for a PHP search engine tutorial, take a look at this YouTube video - it might help.