在编辑模式中，我需要显示PHP下拉列表中的选定值

I have a dropdown in php the value is coming from database. In the edit mode i need to show selected value in to drop down. My php is below:

 <?php
 echo "<td width='5%'>";
 $sql_currency = "SELECT * FROM currency1";
 $result_currency = mysql_query($sql_currency);
 echo "<select id='currency_change$i' >";
while ($row_currency = mysql_fetch_array($result_currency)) {
echo "<option value=" . $row_currency['currency'] . " data-price=" . $row_currency['rate'] .">" . $row_currency['currency'] ."</option>";

 }
 echo "</select>";
 echo "</td>";
 ?>

Try this code...

<?php

    echo "<td width='5%'>";
    $sql_currency = "SELECT * FROM currency1";
    $result_currency = mysql_query($sql_currency);
    echo "<select id='currency_change$i' >";
    /*
     * selected value
     */
    $selectedValue = ""; // assign that value to this variable
    while ($row_currency = mysql_fetch_array($result_currency)) {
        $selected = "";
       if($row_currency['currency'] == $selectedValue){
           $selected = ' selected="selected" ';
       }
        echo "<option ".$selected." value=" . $row_currency['currency'] . " data-price=" . $row_currency['rate'] . ">" . $row_currency['currency'] . "</option>";
    }
    echo "</select>";
    echo "</td>";
    ?>