Dynamically write the "checked" attribute on only one of several radio buttons

Question

What's a good way to reduce or simplify the following php function to check the applicable input field?

  <?php

  $options = get_option( 'navbar_style', '' );
  
  $right = $left = $fade = '';

  if( isset( $options['style'] ) ) {
    if( $options['style'] == 'right' ) {
      $right = ' checked="checked"';
    }
    if( $options['style'] == 'left' ) {
      $left = ' checked="checked"';
    }
    if( $options['style'] == 'fade' ) {
      $fade = ' checked="checked"';
    }
  }

  ?>

  <label><input type='radio' name='navbar_style[style]' value='right' <?php echo $right; ?> >Right <em>(Default)</em></label>
  <label><input type='radio' name='navbar_style[style]' value='left' <?php echo $left; ?> >Left</label>
  <label><input type='radio' name='navbar_style[style]' value='fade' <?php echo $fade; ?> >Fade</label>

Answer 1

As a programmer, you should keep an eye out for repeating patterns in your code. Clearly there is duplicate HTML markup with minimal textual adjustments. The acronym D.R.Y. means "Don't Repeat Yourself".

Create an array of those dynamic data points then implement a loop to generate the desired markup. This will help to prevent typos and make your script much easier to maintain.

Code: (Demo)

$options = ['style' => 'left'];
  
$radios = [
    'right' => 'Right <em>(Default)</em>',
    'left' => 'Left',
    'fade' => 'Fade',
];

foreach ($radios as $value => $text) {
    printf(
        "<label><input type='radio' name='navbar_style[style]' value='%s'%s>%s</label>\n",
        $value,
        ($options['style'] ?? '') === $value ? ' checked' : '',
        $text
    );
}

Answer 2

You can use dynamic variable setting, but not recommended! See next example for proper use.

$options['style'] = 'left';
$right = $left = $fade = '';

if (in_array($options['style'] ?? '', ['right', 'left', 'fade'])) {
    ${$options['style']} = ' checked="checked"';
}

var_dump($right, $left, $fade);

string(0) ""
string(18) " checked="checked""
string(0) ""

---

A much cleaner way would be this version and use for example $checks['left'] instead of $left.

$checks = [];
foreach (['right', 'left', 'checked'] as $check) {
    $checks[$check] = $options['style'] === $check ? ' checked="checked"' : '';
}

var_dump($checks);

array(3) {
  'right' =>
  string(0) ""
  'left' =>
  string(18) " checked="checked""
  'checked' =>
  string(0) ""
}

Answer 3

You can try this:

$options = get_option( 'navbar_style', '' );
$styles = array('right', 'left', 'fade');

$checked = array_fill_keys($styles, '');
if(isset($options['style']) && in_array($options['style'], $styles)) {
  $checked[$options['style']] = 'checked="checked"';
}

Answer 4

You may also do it like this:

$style = ['right' => '', 'left' => '', 'fade' => ''];
    
if (isset($options['style']) && array_key_exists($options['style'], $style)) {
    $style[$options['style']] = ' checked="checked"';
}

Answer 5

Perhaps more compact to create a function and pass in the options, then it's just a test to see if that option is set and return the corresponding html...

  function styleCheck($option, $options)
  {
      return ($options['style'] ?? '') == $option ? ' checked="checked"' : '';
  }
  ?>

  <label><input type='radio' name='navbar_style[style]' value='right'<?php echo styleCheck('right', $options); ?>>Right <em>(Default)</em></label>
  <label><input type='radio' name='navbar_style[style]' value='left'<?php echo styleCheck('left', $options); ?>>Left</label>
  <label><input type='radio' name='navbar_style[style]' value='fade'<?php echo styleCheck('fade', $options); ?>>Fade</label>