PHP下拉问题

Question

My first question, if not appropriate, please ignore.

I have a drop down coded in php which is used to select a value. The value set is 'Off', 0, 1, 2, ... 179 (ie 181 values in total).

In the beginning, the drop down shows all 181 values correctly.

After the value is selected from drop down, some other button is pressed to call a mysql procedure. On call completion, page is refreshed.

The drop down is supposed to retain the selected value across page refreshes, which it does. User should be allowed to change the values though.

However, after the first page refresh, If I try to select a different value from the drop down, All I see in there is the previously selected value 181 times.

Below is the code, could someone please help fix it.

I am not a php programmer, just trying to fix a glitch that my resource left in there.

<select style="width: 87px; height:35px;color:#113C83;margin-bottom:0;border-right-width:0;" id="angle1">
<option value="Off">Off</option>
<?php
for($i=0;$i<=179;$i++)
{
      if(isset($_SESSION['angle1']))
      {
         ?>
         <option value="<?php echo $_SESSION['angle1']; ?>" selected><?php echo $_SESSION['angle1']; ?></option>
         <?php
      }
      else
      { ?>
     <option value="<?php echo $i; ?>"><?php echo $i; ?></option>
     <?php 
      } 
    } ?>
</select>

Answer 1

This is because you are testing the existance of $_SESSION['angle1'] with isset($_SESSION['angle1'] but not that the value it contains matches the current loop counter $i

This tests correctly, assuming that $_SESSION['angle1'] contains the value of the previous selected angle.

This also simplifies your code considerably by using a ternary operator to make that decision

<select style="width: 87px; height:35px;color:#113C83;margin-bottom:0;border-right-width:0;" id="angle1">
    <option value="Off">Off</option>
<?php
    for($i=0; $i <= 179; $i++) {
        $sel = isset($_SESSION['angle1']) && $_SESSION['angle1'] == $i ? 'selected="selected" : '';

        echo '<option ' . $sel . ' value="' . $i . '">' . $i .'</option>';       
    }
?>

Answer 2

That's because you don't specify the correct condition:

<select style="width: 87px; height:35px;color:#113C83;margin-bottom:0;border-right-width:0;" id="angle1">
<option value="Off">Off</option>
<?php
for($i=0;$i<=179;$i++)
{
      if(isset($_SESSION['angle1']) && ($i == $_SESSION['angle1'])) //when you refresh isset($_SESSION['angle1']) will be always true
      {
         ?>
         <option value="<?php echo $_SESSION['angle1']; ?>" selected><?php echo $_SESSION['angle1']; ?></option>
         <?php
      }
      else
      { ?>
     <option value="<?php echo $i; ?>"><?php echo $i; ?></option>
     <?php 
      } 
    } ?>
</select>