Pull a random category

<?php

$taxonomy = 'category';
$param_type = 'category__in';
$term_args=array(
  'orderby' => 'name',
  'order' => 'ASC',
);
$terms = get_terms($taxonomy,$term_args);

if ($terms) {
  $count = 0;
  $random = rand(0,count($terms)-1);  //get a random number
  foreach( $terms as $term ) {
    $count++;
    if ($count == $random ) {  // only if count is equal to random number display get posts for that category
      $args=array(
        "$param_type" => array($term->term_id),
        'post_type' => 'post',
        'post_status' => 'publish',
        'posts_per_page' => -1,
        'caller_get_posts'=> 1
        );
      $my_query = null;
      $my_query = new WP_Query($args);
      if( $my_query->have_posts() ) {
        echo 'List of Posts in '.$taxonomy .' '.$term->name;
        while ($my_query->have_posts()) : $my_query->the_post(); ?>
          <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
         <?php
        endwhile;
      }
    }
  }
}
wp_reset_query();  // Restore global post data stomped by the_post().

?>

So I can basically just take out the query i had and put this in the place of it?

Yes–or fit the ideas into your existing Template.

Related:
Stepping Into Template Tags
Stepping Into Templates
Template Hierarchy

Thanks Michael, this code is a great little trick!

Using your code above, how could I limit the results to only show posts from a random category that had AT LEAST 4 posts in it?

Much appreciated and thanks

Okay had to fix a little something (it never actually displayed the very first term if that term was the random choice) and add your request:

<?php
$min_count=4; //minimum number of posts in term to consider
$taxonomy = 'category';
$param_type = 'category__in';
$term_args=array(
  'orderby' => 'name',
  'order' => 'ASC',
);
$allterms = get_terms($taxonomy,$term_args);

// only terms that meet our $min_count
if ($allterms) {
  $terms=array();
  foreach( $allterms as $term ) {
    if ($term->count >= $min_count) {
     $terms[]=$term;
    }
  }
}

if ($terms) {
  $random = rand(0,count($terms)-1);  //get a random number from 0 to number of elements in $terms array
  $term=$terms[$random];
  $args=array(
    "$param_type" => array($term->term_id),
    'post_type' => 'post',
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'caller_get_posts'=> 1
    );
  $my_query = null;
  $my_query = new WP_Query($args);
  if( $my_query->have_posts() ) {
    echo 'List of Posts in '.$taxonomy .' '.$term->name;
    while ($my_query->have_posts()) : $my_query->the_post(); ?>
      <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
     <?php
    endwhile;
  }
}
wp_reset_query();  // Restore global post data stomped by the_post().
?>

WOW, thanks Michael for adding the request and fix – this piece of code is very useful and I know will come in handy for many wordpress developers out there – cheers.

hi,
I have this code in my home.php to display category + category icon.
i was wondering if is possible to select the category randomly?

<?php recent_posts('limit=10&included_cats=538'); ?>
<?php get_cat_icon('link=true&class=myicons&cat=538&description=true'); ?>

tried this but something is not right..

<?php
$min_count=4; //minimum number of posts in term to consider
$taxonomy = 'category';
$param_type = 'category__in';
$term_args=array(
'orderby' => 'name',
'order' => 'ASC',
);
$allterms = get_terms($taxonomy,$term_args);

// only terms that meet our $min_count
if ($allterms) {
$terms=array();
foreach( $allterms as $term ) {
if ($term->count >= $min_count) {
$terms[]=$term;
}
}
}

if ($terms) {
$random = rand(0,count($terms)-1); //get a random number from 0 to number of elements in $terms array
$term=$terms[$random];
$args=array(
"$param_type" => array($term->term_id),
'post_type' => 'post',
'post_status' => 'publish',
'posts_per_page' => -1,
'caller_get_posts'=> 1
);
$my_query = null;
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
recent_posts('limit=10&included_cats=$term');

}
}
wp_reset_query(); // Restore global post data stomped by the_post().
?>