Add theme contact options in Wordpress (from http://codex.wordpress.org/Creating_Options_Pages and http://ottopress.com/2009/wordpress-settings-api-tutorial/)

contact-options.php

<?php
  
  // WARNING STILL NEED TO SANITIZE
  
	class MyContactPage {

	    /** Holds the values to be used in the fields callbacks */
	    private $options;
	    private $my_option_name = 'contact_infos';
	    private $my_option_admin_slug = 'contact-informations';

	    /** Automatically calculated variable*/
	    private $option_group = 'contact_infos_options_group_1';
	    private $admin_page_handle = 'contact-informations-admin-page';

	    /** Start up */
	    public function __construct() {
	        add_action( 'admin_menu', array( $this, 'add_option_page' ) );
	        add_action( 'admin_init', array( $this, 'page_init' ) );
	    }

	    /**  Add options page */
	    public function add_option_page() {
	        // This page will appear as top level menu item in the admin
	        // To add it under "Settings" use 'add_options_page'
	        // To add it under any other top level item use 'add_menu_page'
	        add_menu_page(
	            _x('Contact Informations', 'theme-option'), 
	            _x('Contact', 'theme-option'), 
	            'edit_published_pages', //in this case editors can also access the page. To restrict it to admins replace 'with manage_options'
	            $this->my_option_admin_slug,
	            array( $this, 'create_option_page' ),
	            'dashicons-location-alt',
	            21
	        );
	    }

	    /** Options page callback */
	    public function create_option_page() {
	        // Set class property
	        $this->options = get_option( $this->my_option_name  );
	       	
	       	echo '<div class="wrap">';
	       		echo '<h2>'._x('Contact Informations', 'theme-option').'</h2>';
	      		echo '<form method="post" action="options.php">';
	            
	                // This prints out all hidden setting fields
	                settings_fields( $this->option_group );   
	                do_settings_sections( $this->admin_page_handle );
	                submit_button();

	            echo '</form>';
	        echo '</div>';
	    }

	    /** Register and add settings */
	    public function page_init() {        
	        register_setting(
	            $this->option_group, // Option group (used for nonce and other security issues. Must be the same as setting_fields)
	            $this->my_option_name, // Option name
	            array( $this, 'sanitize' ) // Sanitize
	        );

	        add_settings_section(
	            'main_contact_infos', // ID
	            'Main Contact informations', // Title
	            array( $this, 'print_main_contact_info_desc' ), // Callback
	            $this->admin_page_handle // Page

	        );

	        $my_fields = array(
	        	array(
	        		'label' => 'Legal name',
	        		'setting_section_id' => 'main_contact_infos',
	        		'input_type' => 'text',
	        	)
	        );

	        foreach ($my_fields as $input_field) {

	        	$input_id = strtolower ( preg_replace('/[^\da-z]/i', '_', $input_field['label']) );

		        add_settings_field(
		            $input_id, // ID
		            __($input_field['label']), // Title 
		            array( $this, 'render_field' ), // Callback
		            $this->admin_page_handle, // Page
		            $input_field['setting_section_id'], // Section
		            array('input_type'=>$input_field['input_type'], 'input_id' => $input_id)
		        );

	        }

	    }

	    /** Sanitize each setting field as needed */
	    public function sanitize( $input ) {

	    	foreach ($input as $input_id => $value) {
	    		$this->options[$input_id] = trim($value);
	    	}

	        if( isset( $input['id_number'] ) )
	            $this->options['id_number'] = absint( trim($input['id_number']) );


			return $this->options;
	    }

	    /** Print the Section text */
	    public function render_field( $args ) {
	    	$output_value = isset($args[ 'input_id' ]) ? esc_attr($this->options['legal_name']) : '';
	    	$input_type =  isset($args[ 'input_type' ]) ? esc_attr($args[ 'input_type']) : 'text';
	    	
	    	if ($input_type === 'textarea') {
				printf(
					'<textarea id="%s" name="%s[%s]">%s</textarea>',
					$args[ 'input_id' ],
		        	$this->my_option_name,
		        	$args[ 'input_id' ],
		        	$output_value
				);
	    	} else {

		    	printf(
		        	'<input type="%s" id="%s" name="%s[%s]" value="%s" />',
		        	$input_type,
		        	$args[ 'input_id' ],
		        	$this->my_option_name,
		        	$args[ 'input_id' ],
		        	$output_value
		        );
		    }
	    }

	    public function print_main_contact_info_desc() {
	    	echo '<p>'.__('Will be use to generate your contact page and tile (home screen).').'<br><em>'.__('Contact email will receive the messages sent through the contact form').'</em></p>';
	    }

	    /** Get the settings option array and print one of its values */
	    public function id_number_callback() {
	    	$output_value = isset($this->options['id_number']) ? esc_attr($this->options['id_number']) : '';
	        printf(
	        	'<input type="text" id="id_number" name="%s[id_number]" value="%s" class="regular-text" />',
	        	$this->my_option_name,
	        	$output_value
	        );
	    }

	    /** Get the settings option array and print one of its values */
	    public function title_callback() {
	    	$output_value = isset($this->options['title']) ? esc_attr($this->options['title']) : '';
	        printf(
	        	'<input type="text" id="title" name="%s[title]" value="%s" />',
	        	$this->my_option_name,
	        	$output_value
	        );
	    }
	}

	if( is_admin() )
	    $my_settings_page = new MyContactPage();
?>