php html。 如何在<option>中显示用户存储的db值？ [关闭]

Question

This will be shown on the user settings page.

(example)

       <select>
          <option value="0">0</option>
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="3">3</option>
          <option value="4">4</option>

       </select> 

If the user has value 3 stored in the db then i want the option-dropdown to show value 3 when the user is on the settings page. How can i do that?

Answer 1

First, you need to get that value from the database. I'll use MySQLi in this example.

<?php
    // Connecting to the database
    $mysqli = new mysqli($mysql_hostname, $mysql_username, $mysql_password, $mysql_dbname);
    if ($mysqli->connect_errno) {
        echo "Failed to connect to MySQL: (".$mysqli->connect_errno.") ".$mysqli->connect_error;
    }
    $mysqli->set_charset("utf8");

    $result = $mysqli->query("SELECT * FROM users");

    // Getting the row
    while ($row = $result->fetch_assoc()) {
        $valueFromDB = $row['columName'];
    }
?>

<select>
    <option value="0" <?php if ($valueFromDB == "0") {echo " selected";} ?>>0</option>
    <option value="1" <?php if ($valueFromDB == "1") {echo " selected";} ?>>1</option>
    <option value="2" <?php if ($valueFromDB == "2") {echo " selected";} ?>>2</option>
    <option value="3" <?php if ($valueFromDB == "3") {echo " selected";} ?>>3</option>
    <option value="4" <?php if ($valueFromDB == "4") {echo " selected";} ?>>4</option>
</select>

This is a series of if-statements. There are probably other was of going around this, but this will work.

EDIT: As you commented, this is a lot of work if you have many lines of options. If that's the case, you can use the following code to make PHP generate them.

<select>
    <?php 
    $numRows = 30; // This is the number of options values you output
    for ($i=0; $i < $numRows; $i++) {
        echo "<option value=\"$i\"";
        if ($valueFromDB == "$i") 
            echo " selected"; 
        echo ">$i</option>";
    }
?>
</select>

This will output options equal to the value of $numRows. Note that it starts counting at 0.