Problem with database manipulation

I’m making a plugin for any visitor manipulate data in the database I created via shortcode, but occurs the error “Fatal error: Call to undefined function add_filter () in … wp-admin \ includes \ plugin.php on line 1691 “. Does anyone have any suggestions or solution? Below is one example

—– In the file cidade.php I have

<?php

/*
Plugin Name: Teste
Plugin URI: http://www.unii.com.br
Description: Create[x], Read[x], Update[x], Delete[ x] dados em uma tabela
Author: UNII Web Technology
Version: 1.0
Author URI: http://www.unii.com.br
*/

define( ‘PLUGIN_PATH’, plugin_dir_path(__FILE__) );
require_once ( PLUGIN_PATH . ‘/includes/functions.php’);

require_once ( ABSPATH . ‘/wp-admin/includes/plugin.php’ );

add_action( ‘admin_menu’, ‘adiciona_menu’ );

add_shortcode( ‘lista_cidade’, ‘home_cidade’ );

?>

—– In the functions.php file I have
<?php
define( ‘PLUGIN_PATH’, plugin_dir_path(__FILE__) );
require_once ( PLUGIN_PATH . ‘/includes/forms.php’);

require_once ( ABSPATH . ‘/wp-admin/includes/plugin.php’ );

function adiciona_menu() {

add_menu_page( ‘teste’,’teste’, ‘manage_options’,
‘teste-menu’, ‘options_default’, plugins_url( ‘icon.png’, __FILE__ ) );

add_submenu_page( ‘teste-menu’,’Cidade’, ‘Cidade’,
‘manage_options’, ‘cidade’, ‘home_cidade’ );
}

?>

—– In the file forms.php I have
<?php

require_once ( ABSPATH . ‘/wp-admin/includes/plugin.php’ );

function home_cidade () {

<form method=”post” action=”<?php echo plugins_url(‘crud.php’, __FILE__); ?>”>
<input type=”hidden” name=”func” value=”salvar_cidade” />
<input type=”hidden” name=”current_url” value=”<?php echo the_permalink(); ?>”/>

<table class=”wp-list-table widefat fixed” >
<tr>
<td style=”width: 100px”>Cidade</td>
<td><input type=”text” name=”cidade” size=”60″ /></td>
</tr>
</table>

<input type=”submit” value=”salvar” class=”button-primary”/>
</form>
}

?>

—– In the file crud.php I have

<?php

require_once (‘../../../../wp-admin/includes/plugin.php’ );

if (isset ($_POST[‘cidade’])) {

global $wpdb;
$cidade_data = array();
$cidade_data[‘cidade’]=( isset( $_POST[‘cidade’] ) ? $_POST[‘cidade’] : ” );
$curr_url = ( isset( $_POST[‘current_url’] ) ? $_POST[‘current_url’] : ” );

$wpdb->query( $wpdb->prepare( “INSERT INTO cidade(cidade) VALUES (%s)”,$cidade_data[‘cidade’]));

wp_redirect( $curr_url);
exit;
}
?>