Taxonomy custom fields. Handles only text and media fields. Values are saved inside the options table.

TaxField.php

<?php
namespace Themosis\Taxonomy;

/**
 * TaxField class
 * 
 * Allow the user to add custom fields to a taxonomy.
*/

class TaxField
{   
    /**
     * The taxonomy slug.
     *
     * @var string
     * @access private
     */
    private $slug;
    
    /**
     * Tell if the taxonomy exists.
     *
     * @var boolean
     * @access private
     */
    private $exists = false;
    
    /**
     * The custom fields of the taxonomy.
     *
     * @var array
     * @access private
     */
    private $fields = array();

    /**
     * The TaxField constructor.
     *
     * @param string $taxonomySlug The taxonomy slug used by action hooks.
     */
    private function __construct($taxonomySlug)
    {   
        $this->slug = $taxonomySlug;
        
        /*-----------------------------------------------------------------------*/
        // Check if the taxonomy exists before going further.
        /*-----------------------------------------------------------------------*/
    	add_action('wp_loaded', array($this, 'check'));
    }

    /**
     * Init the custom taxonomy field.
     *
     * @param string $taxonomySlug The taxonomy slug.
     * @throws TaxonomyException
     * @return \Themosis\Taxonomy\TaxField
     */
    public static function make($taxonomySlug)
    {   
        $slug = trim($taxonomySlug);
        
        if (!empty($slug) && is_string($slug)) {
        
            return new static($slug);
            
        } else {
            
            throw new TaxonomyException("String expected as a parameter.");
            
        }
    }

    /**
     * Check if the taxonomy exists. Call by the action hook 'wp_loaded'.
     * If not, throw an exception.
     *
     * @throws TaxonomyException
     * @return void
     * @ignore
     */
    public function check()
    {
    	if (taxonomy_exists($this->slug)) {
        	
        	/*-----------------------------------------------------------------------*/
        	// Set the exists property to true.
        	// Allow the user to define the fields later with the "set" method.
        	/*-----------------------------------------------------------------------*/
        	$this->exists = true;
        	
    	} else {
        	
        	throw new TaxonomyException('The taxonomy slug "'.$this->slug.'" does not exists.');
        	
    	}
    }

    /**
     * Set the custom fields for the taxonomy.
     *
     * @param array $fields A list of fields.
     * @throws TaxonomyException
     * @return \Themosis\Taxonomy\TaxField
     */
    public function set(array $fields)
    {        
        if (is_array($fields) && !empty($fields)) {
            
            /*-----------------------------------------------------------------------*/
        	// Parse the fields and save them to the instance property.
        	/*-----------------------------------------------------------------------*/
        	$this->fields = $this->parse($fields, $this->slug);
        	
        	/*-----------------------------------------------------------------------*/
            // Add the field to the "add term page"
            // {$taxonomy_slug}_add_form_fields
            /*-----------------------------------------------------------------------*/
            $slug = $this->slug.'_add_form_fields';
            
            add_action($slug, array($this, 'addFields'));
            
            /*-----------------------------------------------------------------------*/
            // Add the field to the "edit term page"
            /*-----------------------------------------------------------------------*/
            $slug = $this->slug.'_edit_form_fields';
            
            add_action($slug, array($this, 'editFields'));
            
            /*-----------------------------------------------------------------------*/
            // Register the save hooks on the add + edit pages.
            /*-----------------------------------------------------------------------*/
            add_action('edited_'.$this->slug, array($this, 'save'), 10, 2);
            add_action('create_'.$this->slug, array($this, 'save'), 10, 2);
            
            /*-----------------------------------------------------------------------*/
            // Register the delete hook in order to remove the custom fields
            // from the options table.
            /*-----------------------------------------------------------------------*/
            add_action('delete_term', array($this,'delete'), 10,2);
            
            return $this;
        	
        } else {
            
            throw new TaxonomyException('Array expected as a parameter.');
            
        }
    }
    
    /**
     * Display the custom fields on the add terms page.
     *
     * @return void
     * @ignore
     */
    public function addFields()
    {
    	/*-----------------------------------------------------------------------*/
    	// Output the custom fields
    	/*-----------------------------------------------------------------------*/
    	TaxFieldRenderer::render('add', $this->fields);
    }

    /**
     * Display the custom fields on the edit term page.
     *
     * @param \stdClass $term The term object passed by WordPress.
     * @return void
     * @ignore
     */
    public function editFields(\stdClass $term)
    {
    	/*-----------------------------------------------------------------------*/
    	// Output the custom fields
    	/*-----------------------------------------------------------------------*/
    	TaxFieldRenderer::render('edit', $this->fields, $term);
    }
    
    /**
     * Save the fields values in the options table.
     *
     * @param int $term_id The term ID.
     * @return void
     * @ignore
     */
    public function save($term_id)
    {    	
    	if (isset($_POST[$this->slug])) {
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Option unique key
    	    /*-----------------------------------------------------------------------*/
    	    $optionKey = $this->slug.'_'.$term_id;
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Retrieve an existing value if it exists...
    	    /*-----------------------------------------------------------------------*/
    		$term_meta = get_option($optionKey);
    		
    		/*-----------------------------------------------------------------------*/
    		// Get all fields names's key
    		/*-----------------------------------------------------------------------*/
    		$cat_keys = array_keys($_POST[$this->slug]);
    		
    		foreach ($cat_keys as $key) {
    		
    			if (isset($_POST[$this->slug][$key])) {
    			
    				$term_meta[$key] = $_POST[$this->slug][$key];
    				
    			}
    			
    		}
    		
    		/*-----------------------------------------------------------------------*/
    		// Save the fields
    		/*-----------------------------------------------------------------------*/
    		update_option($optionKey, $term_meta );
    	}
    }

    /**
     * Delete the fields from the database.
     *
     * @param \stdClass $term The term object.
     * @param int $term_id The term ID.
     * @return void
     * @ignore
     */
    public function delete(\stdClass $term, $term_id)
    {
        $key = $this->slug.'_'.$term_id;
        
    	delete_option($key);
    }
    
    /**
     * Parse the fields and mix them with a default one.
     *
     * @param array $fields The defined fields and their properties.
     * @param string $taxonomySlug The taxonomy slug.
     * @return array The parsed array of fields with a TaxonomySlug key/value.
     */
    private function parse(array $fields, $taxonomySlug)
	{
		$newFields = array();

		foreach ($fields as $field) {
			
			$defaults = array(
				'name'              => 'default_field',
				'title'             => ucfirst($field['name']),
				'info'              => '',
				'default'           => '',
				'type'              => 'text',
				'options'           => array(),
				'class'             => '',
				'multiple'	        => false,
				'fields'	        => array(),
				'taxonomy_slug'     => $taxonomySlug
			);

			/*-----------------------------------------------------------------------*/
			// Mix values from defaults and $args and then extract
			// the results as $variables
			/*-----------------------------------------------------------------------*/
			extract(wp_parse_args($field, $defaults));

			$field_args = array(
				'type'              => $type,
				'name'              => $name,
				'info'              => $info,
				'default'           => $default,
				'options'           => $options,
				'label_for'         => $name,
				'class'             => $class,
				'title'		        => $title,
				'multiple'	        => $multiple,
				'fields'	        => $fields,
				'taxonomy_slug'     => $taxonomy_slug
			);

			/*-----------------------------------------------------------------------*/
			// Add new settings
			/*-----------------------------------------------------------------------*/
			$newFields[] = $field_args;

		}

		return $newFields;
	}
    
}

TaxFieldRenderer.php

<?php
namespace Themosis\Taxonomy;

/**
 * TaxFieldRenderer class
 *
 * Utility class that output html in order to display
 * the custom fields of the taxonomies.
 *
*/
class TaxFieldRenderer
{

    /**
     * Handle output for the "add term" page.
     *
     * @param string $typeOfPage Type of the page where to output the field - Accepted values : 'add', 'edit'.
     * @param array $fields The fields to output.
     * @param \stdClass $term The term object sent by WordPress.
     * @return void
     */
    public static function render($typeOfPage, array $fields, \stdClass $term = null)
    {        
        foreach ($fields as $field):
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Output the custom field
    	    /*-----------------------------------------------------------------------*/
            switch ($field['type']) {
                
                /*-----------------------------------------------------------------------*/
                // Text input field
                /*-----------------------------------------------------------------------*/
                case 'text':
                    
                    static::text($typeOfPage, $field, $term);
                    
                    break;
                
                /*-----------------------------------------------------------------------*/
                // Media custom field
                /*-----------------------------------------------------------------------*/
                case 'media':
                
                    static::media($typeOfPage, $field, $term);
                
                    break;
                default:
                    break;
            }
    	    
    	endforeach;
    }
    
    /**
     * Helper function that checks the page type.
     *
     * @param string $typeOfPage Type of the page: 'add' or 'edit'.
     * @return bool True. False if not the 'add' page.
     */
    private static function isAddPage($typeOfPage)
    {
    	if ($typeOfPage === 'add') {
        	return true;
    	}
    	
    	return false;
    }
    
    /**
     * Open tags for the 'Add term' page.
     *
     * @param string $name The name attribute of the custom field.
     * @param string $title The title property of the custom field.
     * @return void
     */
    private static function openTagsForAddPage($name, $title)
    {
        ?>
        
    	<div class="form-field">
                <label for="<?php echo($name); ?>-field"><?php echo($title); ?></label>
                
        <?php
    }
    
    /**
     * Close tags for the 'Add term' page.
     *
     * @return void
     */
    private static function closeTagsForAddPage()
    {
    	?>
    	
    	</div>
    	
    	<?php
    }
    
    /**
     * Open tags for the 'Edit term' page.
     *
     * @param string $name The name attribute of the custom field.
     * @param string $title The title property of the custom field.
     * @return void
     */
    private static function openTagsForEditPage($name, $title)
    {
    	?>
    	
    	<tr class="form-field">
    	        <th scope="row" valign="top">
    	            <label for="<?php echo($name); ?>-field"><?php echo($title); ?></label>
    	        </th>
    	        <td>
    	
    	<?php
    }
    
    /**
     * Close tags for the 'Edit term' page.
     *
     * @return void
     */
    private static function closeTagsForEditPage()
    {
    	?>
	        </td>
        </tr>
        
    	<?php
    }
    
    /**
     * Display the 'info' html tags.
     *
     * @param string $typeOfPage Type of page: 'edit' or 'add'.
     * @param string $info The info text to display.
     * @return void
     */
    private static function infos($typeOfPage, $info)
    {
        /*-----------------------------------------------------------------------*/
        // ADD page description
        /*-----------------------------------------------------------------------*/
    	if (static::isAddPage($typeOfPage)) {
        	
            if (isset($info) && !empty($info)):
            
            ?>
            
                <p><?php echo(ucfirst($info)); ?></p>
                
            <?php
        
            endif;
            
        /*-----------------------------------------------------------------------*/
        // EDIT page description
        /*-----------------------------------------------------------------------*/	
    	} else {
        	
        	
            if (isset($info) && !empty($info)):
            
            ?>
        
                <span class="description"><?php echo(ucfirst($info)); ?></span>
            
            <?php
        
            endif;
        	
    	}
    }

    /**
     * Render a text field.
     *
     * @param string $typeOfPage Which page is viewed: 'add' or 'edit'.
     * @param array $field The field properties.
     * @param \stdClass $term The term object sent by WordPress.
     * @return void
     */
    private static function text($typeOfPage, array $field, \stdClass $term = null)
    {
        extract($field);
        
        /*-----------------------------------------------------------------------*/
        // HTML output for the add term page.
        /*-----------------------------------------------------------------------*/
    	if (static::isAddPage($typeOfPage)):
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Open tags
    	    /*-----------------------------------------------------------------------*/
    	    static::openTagsForAddPage($name, $title);
    	    
            ?>
            
            <input type="text" id="<?php echo($name); ?>-field" name="<?php echo($taxonomy_slug.'['.$name.']'); ?>" value="" size="40"/>
            
            <?php
            
            /*-----------------------------------------------------------------------*/
            // Infos
            /*-----------------------------------------------------------------------*/
            static::infos($typeOfPage, $info);
            
            /*-----------------------------------------------------------------------*/
            // Close tags
            /*-----------------------------------------------------------------------*/
            static::closeTagsForAddPage();
        
        /*-----------------------------------------------------------------------*/
        // HTML output for the edit term page.
        /*-----------------------------------------------------------------------*/
    	else:
    	
    	    /*-----------------------------------------------------------------------*/
    	    // Retrieve the value for this field if it exists.
    	    /*-----------------------------------------------------------------------*/
    	    $optionkey = $taxonomy_slug.'_'.$term->term_id;
    	    
    	    // Array of values of all taxonomy fields.
    	    $values = get_option($optionkey);
    	    // Get the field value and check if it is set.
    	    $value = isset($values[$name]) ? $values[$name] : '';
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Open tags
    	    /*-----------------------------------------------------------------------*/
    	    static::openTagsForEditPage($name, $title);
    	    
    	    ?>
	            <input type="text" id="<?php echo($name); ?>-field" name="<?php echo($taxonomy_slug.'['.$name.']'); ?>" value="<?php if (isset($value) && !empty($value)) { echo($value); } ?>" size="40" />
	            <br />
	            
	            <?php
	            
	            /*-----------------------------------------------------------------------*/
	            // Infos
	            /*-----------------------------------------------------------------------*/
	            static::infos($typeOfPage, $info);
	            
    	    /*-----------------------------------------------------------------------*/
    	    // Close tags
    	    /*-----------------------------------------------------------------------*/
    	    static::closeTagsForEditPage();
    	    
    	endif;
    }

    /**
     * Render a Media field.
     *
     * @param string $typeOfPage Which page is viewed: 'add' or 'edit'.
     * @param array $field The field properties.
     * @param \stdClass $term The term object sent by WordPress.
     * @return void
     */
    private static function media($typeOfPage, array $field, \stdClass $term = null)
    {
    	extract($field);
    	
    	/*-----------------------------------------------------------------------*/
        // HTML output for the add term page.
        /*-----------------------------------------------------------------------*/
    	if (static::isAddPage($typeOfPage)):
    	
    	    /*-----------------------------------------------------------------------*/
    	    // Open tags
    	    /*-----------------------------------------------------------------------*/
    	    static::openTagsForAddPage($name, $title);
    	
    	    ?>
    	    
    	    <table class="themosis-media-table">
					
				<tbody>
				
					<tr class="themosis-field-media">
					
						<td class="themosis-media-input">
						    <input type="text" size="40" name="<?php echo($taxonomy_slug.'['.$name.']'); ?>" id="<?php echo($name); ?>-field" />
						</td>
						
						<td>
						    <button type="button" class="button-primary themosis-media-button" id="themosis-media-add"><?php _e('Add', THEMOSIS_FRAMEWORK_TEXTDOMAIN); ?></button>
						</td>
						
						<td>
						    <button type="button" class="button themosis-media-clear" id="themosis-media-clear"><?php _e('Clear', THEMOSIS_FRAMEWORK_TEXTDOMAIN); ?></button>
						</td>
						
					</tr>
					
				</tbody>
				
			</table>
    	    
    	    <?php
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Infos
    	    /*-----------------------------------------------------------------------*/
    	    static::infos($typeOfPage, $info);
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Close tags
    	    /*-----------------------------------------------------------------------*/
    	    static::closeTagsForAddPage();
    	
    	/*-----------------------------------------------------------------------*/
        // HTML output for the edit term page.
        /*-----------------------------------------------------------------------*/
    	else:
    	
    	    /*-----------------------------------------------------------------------*/
    	    // Retrieve the value for this field if it exists.
    	    /*-----------------------------------------------------------------------*/
    	    $optionkey = $taxonomy_slug.'_'.$term->term_id;
    	    
    	    // Array of values of all taxonomy fields.
    	    $values = get_option($optionkey);
    	    // Get the field value and check if it is set.
    	    $value = isset($values[$name]) ? $values[$name] : '';
    	
    	    /*-----------------------------------------------------------------------*/
    	    // Open tags
    	    /*-----------------------------------------------------------------------*/
    	    static::openTagsForEditPage($name, $title);
    	    
    	    ?>
    	    
    	    <table class="themosis-media-table">
					
				<tbody>
				
					<tr class="themosis-field-media">
					
						<td class="themosis-media-input">
						    <input type="text" size="40" name="<?php echo($taxonomy_slug.'['.$name.']'); ?>" id="<?php echo($name); ?>-field" value="<?php if (isset($value) && !empty($value)) { echo($value); } ?>" />
						</td>
						
						<td>
						    <button type="button" class="button-primary themosis-media-button" id="themosis-media-add"><?php _e('Add', THEMOSIS_FRAMEWORK_TEXTDOMAIN); ?></button>
						</td>
						
						<td>
						    <button type="button" class="button themosis-media-clear" id="themosis-media-clear"><?php _e('Clear', THEMOSIS_FRAMEWORK_TEXTDOMAIN); ?></button>
						</td>
						
					</tr>
					
				</tbody>
				
			</table>
    	    
    	    <?php
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Infos
    	    /*-----------------------------------------------------------------------*/
    	    static::infos($typeOfPage, $info);
    	    
    	    /*-----------------------------------------------------------------------*/
    	    // Close tags
    	    /*-----------------------------------------------------------------------*/
    	    static::closeTagsForEditPage();
    	
    	endif;
    }
    
}