WordPress Plugin: Add custom search fields to the term editor.

term-editor-search-field.php

<?php
/**
 * Plugin Name:  Term Editor Search Field
 * Description:  Adds Search fields to the term editor.
 * Plugin URI:   https://gist.github.com/birgire/22a57ad1eed45e366cc1d47575bba0b1
 * Author:       birgire
 * Version:      1.0.2
 */

/**
 *  Setup custom term editor fields
 */
add_action( 'load-term.php', function()
{
	/**
	 * Multiple Search Links
	 */
	$fieldGoogle = new TermEditorSearchField;

	// Adjust to your needs
	$fieldGoogle
		->setFieldLabel( 'Search' )
		->setFieldDescription( '' )
		->setSearchApi( 'https://www.google.de/search/?q=TERMNAME+logo&tbm=isch' )
		->setSearchApi( 'https://duckduckgo.com/?q=TERMNAME+logo' )
		->setSearchApi( 'https://plus.google.com/s/TERMNAME' )
		->display( 'post_tag' );
		
} );


/**
 * Class TermEditorSearchField
 * @since 1.0.0
 */
class TermEditorSearchField
{	
	private $urls;
	private $label;
	private $description;
	
	/**
	 * Collect search api urls
	 * 
	 * @param string $url
	 * @return TermEditorSearchField
	 */
	public function setSearchApi( $url = '' )
	{
		$this->urls[] = $url;
		return $this;
	}

	/**
	 * Set field label
	 * 
	 * @param string $label
	 * @return TermEditorSearchField
	 */
	public function setFieldLabel( $label = '' )
	{
		$this->label = $label;
		return $this;
	}

	/**
	 * Set field description
	 * 
	 * @param string $description
	 * @return TermEditorSearchField
	 */
	public function setFieldDescription( $description = '' )
	{
		$this->description = $description;
		return $this;
	}

	/**
	 * Get Search Requests for a single term
	 * 
	 * @param \WP_Term $term
	 * @return array $requests
	 */
	public function getSearchRequestsForTerm( \WP_Term $term )
	{
		// Generate requests 
		foreach( $this->urls as $key => $url )
		{
			$url = str_replace( 
				array(  'TERMNAME', 'TERMSLUG' ),
				array( $term->name, $term->slug ), 
				$url 
			);
			$requests[] = $url;
		}
		
		return $requests;
	}

	/**
	 * Display by hooking into the dynamic {$term}_edit_form_fields filter
	 * 
	 * @param string $term
	 * @return void
	 */
	public function display( $term = 'post_tag' )
	{
		add_filter( "{$term}_edit_form_fields", array( $this, 'add_field' ), 10, 2 );
	}
	
	/**
	 * Add table field
	 * 
	 * @param \WP_Term $term
	 * @param array $taxonomy
	 * @return void
	 */
	public function add_field( $term, $taxonomy )
	{		
		if( ! (  $term instanceof \WP_Term ) )
			return;
	
		// Generate the search links list	
		$li = '';
		$requests = $this->getSearchRequestsForTerm( $term );
		foreach( (array) $requests as $request )
		{
			$li .= sprintf( 
				'<li><a href="%s" target="blank">%s</a></li>',
				esc_url( $request ),
				esc_url( $request )
			);
		}
	
		// Display the table field
		printf( 
			'<tr class="form-field term-search-wrap">
				<th scope="row"><label for="search">%s</label></th>
				<td>
					<ul class="term-search-list">%s</ul> 
					<p class="description">%s</p></td>
				</td>
			</tr>',
			esc_html( $this->label ),
			$li,
			esc_html( $this->description )
		);	
		
	}
	
} // end class