Checkbox default unchecked - php

Question

For my Wordpress plugin option page I want to use checkboxes to set the options. I'm using this code to add it to the option page and it works well. Except that I want the checkboxes default set to unchecked. How do I do this?
public function id_number_callback()
{
printf(
'<input id="%1$s" name="cus_func_option[%1$s]" type="checkbox" %2$s" />',
'add_image_dimesions',
checked( isset( $this->options['add_image_dimesions'] ), true, false )
);
Edit: The full code I want to use is this
class MySettingsPage
{
/**
* Holds the values to be used in the fields callbacks
*/
private $options;
/**
* Start up
*/
public function __construct()
{
add_action( 'admin_menu', array( $this, 'add_plugin_page' ) );
add_action( 'admin_init', array( $this, 'page_init' ) );
}
/**
* Add options page
*/
public function add_plugin_page()
{
// This page will be under "Settings"
add_options_page(
'Settings Admin',
'Custom functions',
'manage_options',
'cus-func-admin',
array( $this, 'create_admin_page' )
);
}
/**
* Options page callback
*/
public function create_admin_page()
{
// Set class property
$this->options = get_option( 'cus_func_option' );
?>
<div class="wrap">
<?php screen_icon(); ?>
<h2>Custom Functions</h2>
<form method="post" action="options.php">
<?php
// This prints out all hidden setting fields
settings_fields( 'cus_func_group' );
do_settings_sections( 'cus-func-admin' );
submit_button();
?>
</form>
</div>
<?php
}
/**
* Register and add settings
*/
public function page_init()
{
register_setting(
'cus_func_group', // Option group
'cus_func_option', // Option name
array( $this, 'sanitize' ) // Sanitize
);
add_settings_section(
'setting_section_id', // ID
'Which Custom Functions do you want to use?', // Title
array( $this, 'print_section_info' ), // Callback
'cus-func-admin' // Page
);
add_settings_field(
'add_image_dimesions', // ID
'Add image dimesions to the Media Page', // Title
array( $this, 'id_number_callback' ), // Callback
'cus-func-admin', // Page
'setting_section_id' // Section
);
add_settings_field(
'title',
'Title',
array( $this, 'title_callback' ),
'cus-func-admin',
'setting_section_id'
);
}
/**
* Sanitize each setting field as needed
*
* #param array $input Contains all settings fields as array keys
*/
public function sanitize( $input )
{
$new_input = array();
if( isset( $input['add_image_dimesions'] ) )
$new_input['add_image_dimesions'] = absint( $input['add_image_dimesions'] );
if( isset( $input['title'] ) )
$new_input['title'] = sanitize_text_field( $input['title'] );
return $new_input;
}
/**
* Print the Section text
*/
public function print_section_info()
{
print 'Pick your Custom Functions below:';
}
/**
* Get the settings option array and print one of its values
*/
public function id_number_callback()
{
printf(
'<input id="%1$s" name="cus_func_option[%1$s]" type="checkbox" %2$s" />',
'add_image_dimesions',
checked( isset( $this->options['add_image_dimesions'] ), true, false )
);
}
/**
* Get the settings option array and print one of its values
*/
public function title_callback()
{
printf(
'<input id="%1$s" name="cus_func_option[%1$s]" type="checkbox" %2$s />',
'title',
checked( isset( $this->options['title'] ), true, false )
);
}
}
if( is_admin() )
$my_settings_page = new MySettingsPage();

Answer 1

Refer to the WordPress Documentation for checked
What is the value of isset( $this->options['add_image_dimesions'] ) in your code?
This is what is determining whether it's checked or not.

Answer 2

If you want the checkbox to always be unchecked when the page is loaded, then you can just remove the second printf token, %2$2, and the second argument to printf, checked( isset( $this->options['add_image_dimesions'] ), true, false ), which will give you this:
public function id_number_callback()
{
printf(
'<input id="%1$s" name="cus_func_option[%1$s]" type="checkbox" />',
'add_image_dimesions'
);