How to set the drop-down list to be selected by default in php

This article mainly introduces how to set the default selected value of the drop-down list (select) in PHP.

For drop-down lists, in HTML, we usually define it like this:

<select name="fruit">
  <option value="apple">苹果</option>
  <option value="banana">香蕉</option>
  <option value="orange">橙子</option>
</select>

In PHP, we set the default selected value by setting the selected attribute of option.

First, we need to get the selected value in the submitted form. Here, we assume there is a form item named fruit. We can use $_POST['fruit'] to get its value. If the form is not submitted, we can set a default value, such as:

$default_fruit = 'apple';

Next, we check in each option whether its value is equal to the value we obtained. If equal, we set the option to the selected state. .

<select name="fruit">
  <option value="apple"<?php if ($_POST[&#39;fruit&#39;] == &#39;apple&#39;) {echo &#39; selected&#39;;} ?>>苹果</option>
  <option value="banana"<?php if ($_POST[&#39;fruit&#39;] == &#39;banana&#39;) {echo &#39; selected&#39;;} ?>>香蕉</option>
  <option value="orange"<?php if ($_POST[&#39;fruit&#39;] == &#39;orange&#39;) {echo &#39; selected&#39;;} ?>>橙子</option>
</select>

In the above code, we add a PHP if judgment in front of the selected attribute of each option. If the value in the form is equal to the value of the current option, we output 'selected', indicating that the option is selected.

As you can see, here we use a method similar to embedded HTML to output HTML in PHP. Although this method is convenient, it is also error-prone and difficult to maintain. If this method is too complicated, we can also use PHP's echo to output HTML, as shown below:

<select name="fruit">
  <?php
    $fruits = array(
      &#39;apple&#39; => '苹果',
      'banana' => '香蕉',
      'orange' => '橙子'
    );
    foreach ($fruits as $value => $label) {
      $selected = ($value == $_POST['fruit']) ? ' selected' : '';
      echo "<option value=\"$value\"$selected>$label</option>";
    }
  ?>
</select>

In the above code, we use an associative array to store the value and label of each option. Use a foreach loop to iterate and output HTML. When outputting option, we use PHP's ternary operator to set the selected attribute on the corresponding option.

In short, setting the default selected drop-down list in PHP is very simple. You only need to check the value of the form item and set the selected attribute of the corresponding option.

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