Alternating between even and odd in a while loop in PHP

问题

Hey guys, Been working on couple of lines of code but I can't seem to get it to work. Basically I want to alternate between even and odd table-styles via a while loop. What am I doing wrong? Seems as though it only loops through the if() everytime.

Thanx!

<?php
    include 'connect.php';
    echo "<table id='hor-zebra'>";
    $i = 0;
    while($row = mysql_fetch_array($result))
    {
       if(i%2 == 0)
       {
          echo "<tr class='even'>";
          echo "<td>" . $row['departure'] ." ✈ ". $row['destination'] . "</td>";
          echo "</tr>";
       }

       else
       {
          echo "<tr>";
          echo "<td>" . $row['departure'] ." ✈ ". $row['destination'] . "</td>";
          echo "</tr>";
       }
       $i++;
    }
    echo "</table>";

    mysql_close($con);

  ?>

回答1:

You have a typo in your if condition. It should be:

   if($i%2 == 0)

You can also save a few keystrokes by just assigning the class name to a variable in the if and else blocks:

   if($i%2 == 0)
   {
      $class = 'even';
   }
   else
   {
      $class = 'odd';
   }

   echo "<tr class='$class'>";
   echo "<td>" . $row['departure'] ." ✈ ". $row['destination'] . "</td>";
   echo "</tr>";

回答2:

you can also use the css .nth-child property

   tr:nth-child(even) {background: #CCC}
tr:nth-child(odd) {background: #FFF}

As per W3 example

回答3:

CSS-Tricks has posted a very very elegant solution to this problem. It appears like super-reductionist C++ magic. Essentially they do this:

<div class="example-class<?php echo ($xyz++%2); ?>">

This works in any loop: for, foreach and while. Modifying the integer gives you larger step sizes, i.e. reset after 3, reset after 4 and so on.

CSS-Tricks final solution

回答4:

You forgot a '$'

 if(i%2 == 0)

Should be

 if(($i % 2) == 0)

回答5:

Replace this line...

if(i%2 == 0)

...with the following:

if($i % 2 == 0)

回答6:

This can be improved further.

foreach($post_array as $array => $row) {
    $class = ($array %2 == 0) ? 'even' : 'odd';
    echo '
    <tr class="'.$class.'">
        <td>' .$row['title']. '</td>
        <td>' .$row['content']. '</td>
        <td>' .$row['catid']. '</td>
        <td>' .$row['id']. '</td>
        <td>' . '<form action="edit.php?id='.$row['id'].'" method="post">
            <input type="hidden" name="id" id="id" value="'.$row['id'].'" />
            <input type="submit" name="edit" value="Edit" />
        </form>' . '</td>
        <td>' . '<form action="" method="post">
            <input type="hidden" name="id" id="id" value="'.$row['id'].'" />
            <input type="submit" name="delete" value="Delete" />
        </form>' . '</td>
    </tr>';
}

来源：https://stackoverflow.com/questions/6112624/alternating-between-even-and-odd-in-a-while-loop-in-php

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php

while-loop