How to remember checkbox choice after submit? - php

Question

I use this code to check which tags are used within a Wordpress category. It renders a checkbox list. I want the form to remember my choice after submit.
This is my code:
<form name="tags" onChange="document.forms.tags.submit();">
<?php
if (is_category()){
$cat = get_query_var('cat');
$yourcat = get_category ($cat);
}
$tag_IDs = array();
query_posts('category_name='.$yourcat->slug);
if (have_posts()) : while (have_posts()) : the_post();
$posttags = get_the_tags();
if ($posttags):
foreach($posttags as $tag) {
if (!in_array($tag->term_id , $tag_IDs)):
$tag_IDs[] = $tag->term_id;
$tag_names[$tag->term_id] = $tag->name;
$tag_slug[$tag->term_id] = $tag->slug;
endif;
}
endif;
endwhile; endif;
wp_reset_query();
if (!empty($tag_IDs)){
echo '<h3>Het meest geschikt voor</h3>';
echo "<input type=\"radio\" name=\"tag\" value=\"\"> Alles weergeven<br>";
}
foreach($tag_IDs as $tag_ID){
echo '<input type="radio" name="tag" value="'.$tag_slug[$tag_ID].'"> '.$tag_names[$tag_ID].'<br>';
}
?>
</form>
Before I was using this code to remember the choice, but it doesn't work with the above code anymore:
if((isset($_GET["tag"])) && $_GET["tag"] == "tag-example") { echo "checked";}
I thought it would work like this, but it doesn't:
echo '<input type="radio" name="tag" value="'.$tag_slug[$tag_ID].'" '.if((isset($_GET["tag"])) && $_GET["tag"] == "oudere-kinderen") { echo "checked";}.'> '.$tag_names[$tag_ID].'<br>';
How can I get the form to remember the checkbox choice?
Solution:
With help from #Jouke I came to this solution:
if (is_category()){
$cat = get_query_var('cat');
$yourcat = get_category ($cat);
}
$tag_IDs = array();
query_posts('category_name='.$yourcat->slug);
if (have_posts()) : while (have_posts()) : the_post();
$posttags = get_the_tags();
if ($posttags):
foreach($posttags as $tag) {
if (!in_array($tag->term_id , $tag_IDs)):
$tag_IDs[] = $tag->term_id;
$tag_names[$tag->term_id] = $tag->name;
$tag_slug[$tag->term_id] = $tag->slug;
endif;
}
endif;
endwhile; endif;
wp_reset_query();
if (!empty($tag_IDs)){
echo '<h3>Het meest geschikt voor</h3>';
echo "<input type=\"radio\" name=\"tag\" value=\"\"> Alles weergeven<br>";
}
foreach($tag_IDs as $tag_ID){
$test = $tag_slug[$tag_ID];
echo '<input type="radio" name="tag" value="'.$test.'"' ;
if((isset($_GET["tag"])) && $_GET["tag"] == $test) {
echo ' checked="checked"';
}
echo '> '.$tag_names[$tag_ID].'<br>';
}

Answer 1

Function(wordpress documentation):
<?php checked( $checked, $current, $echo ); ?>
Example:
<input type='radio' name='tag' value='1' <?php checked(isset($variable)); ?>>variable
Another example(php):
$test=test;
echo "<input type='radio' name='tag' value='$test' checked( isset( $test ) ); >";
With escaping:
$tagslug = $tag_slug[$tag_ID];
echo '<input type="radio" name="tag" value=/"$tagslug/" checked( isset( $tagslug ) );>';
Another example without the wordpress function checked:
Paste it in here and test it
$test = "slug";
echo '<input type="radio" name="tag" value="$test"' ;
if (isset($test)) {
echo 'checked="checked"';
}
echo '>';

Answer 2

Try this
echo '<input type="radio" name="tag" value="'.$tag_slug[$tag_ID].'" '.if((isset($_POST["tag"])) && $_POST["tag"] == "oudere-kinderen") { echo "checked=checked";}.'> '.$tag_names[$tag_ID].'';