PHP下拉列表-添加前导零

Question

I have a simple drop down list:

<select name="day" id="day">
    <?php
       for ($i=1; $i<=31; $i++){
            echo "<option value=\"" . $i . "\">" . $i . "</option>";
       }
     ?>
</select>

What I need to do is add a leading zero to numbers 1 to 9. I don't think I can use sprint or pad here? Any advice welcomed.

Answer 1

Another option

<select name="day" id="day">
    <?php
       for ($i=1; $i<=31; $i++){
            echo "<option value=\"" . str_pad($i, 2, '0', STR_PAD_LEFT) . "\">" . str_pad($i, 2, '0', STR_PAD_LEFT) . "</option>";
       }
     ?>
</select>

Answer 2

您可以使用sprintf("%02d", $number)格式化字符串。

Answer 3

<?php
       $leadingZero;
       for ($i=1; $i<=31; $i++){
           if($i <= 9){
              $leadingZero = 0;
           }
            echo "<option value=\"" . $leadingZero . $i . "\">" . $leadingZero. $i . "</option>";
       }
     ?>

Answer 4

You can make use of str_pad in PHP

<select name="day" id="day">
    <?php
      $leadingZero;
       for ($i=1; $i<=31; $i++){
          if(i<10)
           $leadingZero =  str_pad($leadingZero,1,"0",STR_PAD_LEFT);
          echo "<option value=\"" . $leadingZero . $i . "\">" . $leadingZero. $i . "</option>";
   }
       }
     ?>
</select>