我看到如下一段代码:
……
echo '<table align="center" cellspacing="0" cellpadding="5">
<tr>
<td align="left"><b>Edit</b></td>
<td align="left"><b>Delete</b></td>
<td align="left"><b>Last Name</b></td>
<td align="left"><b>First Name</b></td>
<td align="left"><b>Date Registered</b></td>
</tr>
';
// Fetch and print all the records.
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
echo '<tr>
<td align="left"><a href="edit_user.php?id=' . $row['user_id'] . '">Edit</a></td>
<td align="left"><a href="delete_user.php?id=' . $row['user_id'] . '">Delete</a></td>
<td align="left">' . $row['last_name'] . '</td>
<td align="left">' . $row['first_name'] . '</td>
<td align="left">' . $row['dr'] . '</td>
</tr>
';
} echo '</table>';
……
我的问题是,红色标出的那段代码如何理解?作用是什么?和下面的写法有什么不同?
<td align="left"><a href="edit_user.php?id=$row['user_id'] ">Edit</a></td>
……
echo '<table align="center" cellspacing="0" cellpadding="5">
<tr>
<td align="left"><b>Edit</b></td>
<td align="left"><b>Delete</b></td>
<td align="left"><b>Last Name</b></td>
<td align="left"><b>First Name</b></td>
<td align="left"><b>Date Registered</b></td>
</tr>
';
// Fetch and print all the records.
while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) {
echo '<tr>
<td align="left"><a href="edit_user.php?id=' . $row['user_id'] . '">Edit</a></td>
<td align="left"><a href="delete_user.php?id=' . $row['user_id'] . '">Delete</a></td>
<td align="left">' . $row['last_name'] . '</td>
<td align="left">' . $row['first_name'] . '</td>
<td align="left">' . $row['dr'] . '</td>
</tr>
';
} echo '</table>';
……
我的问题是,红色标出的那段代码如何理解?作用是什么?和下面的写法有什么不同?
<td align="left"><a href="edit_user.php?id=$row['user_id'] ">Edit</a></td>
举例$a = 10;
echo 'there are $a books'; //输出为 there are $a books
echo 'there are'.$a.'books'; //输出为 there are 10 books
echo "there are $a books"; //使用双引号后,输出为 there are 10 books