How to use variables in php in html tags

Use php variables in the html tag, prompt: Undefined index: uid in /var/www//list.php
, the specific code of list.php is as follows:

<code><?php

    require 'redis.php';
    for ($i=0; $i <= ($redis->get("userid")) ; $i++)
    {
        $data[] = $redis->hgetall("user:".$i);
    }
    /* var_dump($data) 的结果如下:
    array (size=3)
  0 => 
    array (size=0)
      empty
  1 => 
    array (size=4)
      'uid' => string '1' (length=1)
      'username' => string 'jjj' (length=3)
      'password' => string '123' (length=3)
      'age' => string '20' (length=2)
  2 => 
    array (size=4)
      'uid' => string '2' (length=1)
      'username' => string 'lamp' (length=4)
      'password' => string '123' (length=3)
      'age' => string '20' (length=2)
      */
?>

<table border="1">
    <caption>user list</caption>
    <tr>
        <th>uid</th>
        <th>username</th>
        <th>age</th>
    </tr>
    <?php foreach ($data as $v) {?>

    <tr>
        <td><?php echo $v['uid'] ?></td>
        <td><?php echo $v['username'] ?></td>
        <td><?php echo $v['age'] ?></td>
    </tr>
    <?php } ?>
</table>
</code>

Reply content:

Use php variables in the html tag, prompt: Undefined index: uid in /var/www//list.php
, the specific code of list.php is as follows:

<code><?php

    require 'redis.php';
    for ($i=0; $i <= ($redis->get("userid")) ; $i++)
    {
        $data[] = $redis->hgetall("user:".$i);
    }
    /* var_dump($data) 的结果如下:
    array (size=3)
  0 => 
    array (size=0)
      empty
  1 => 
    array (size=4)
      'uid' => string '1' (length=1)
      'username' => string 'jjj' (length=3)
      'password' => string '123' (length=3)
      'age' => string '20' (length=2)
  2 => 
    array (size=4)
      'uid' => string '2' (length=1)
      'username' => string 'lamp' (length=4)
      'password' => string '123' (length=3)
      'age' => string '20' (length=2)
      */
?>

<table border="1">
    <caption>user list</caption>
    <tr>
        <th>uid</th>
        <th>username</th>
        <th>age</th>
    </tr>
    <?php foreach ($data as $v) {?>

    <tr>
        <td><?php echo $v['uid'] ?></td>
        <td><?php echo $v['username'] ?></td>
        <td><?php echo $v['age'] ?></td>
    </tr>
    <?php } ?>
</table>
</code>

Can’t I just press isset before echo

The first child element of your array is empty and the uid cannot be found

In many cases in PHP, one thing that needs attention is to have a fault-tolerant mechanism