How do I check if user input in a field in the customizer is a number?

Question

Working on my first theme and thinking about adding some options that are specifically numbers like number of menu levels or number of posts to display on the homepage. Is it possible to check that the input in the customizer is just a number? And perhaps a certain limit like 5 for menu levels and 20 or something for posts on the homepage? Here is the code I'm working on with the customizer api as an example:

$wp_customize->add_setting( 'posts_number_home' , array(
'default'     => '10',
'transport'   => 'refresh',
'sanitize_callback' => 'sanitize_text_field',
) );

$wp_customize->add_control( new WP_Customize_Control( 
$wp_customize, 
'posts_number_home',
array(
    'section'  => 'mytheme_options',
    'settings' => 'posts_number_home',
    'type' => 'text',
    'priority' => 10,
) 
));

Answer 1

You are right. A couple of fixes/suggestions, though.

• You should use absint as a sanitization callback.
• Also, you don't have to explicitly use the WP_Customize_Control class. The number field can be created with the regular syntax you use for the text field with an exception of the type and additional attributes.
• Another thing is that you don't have to define the refresh transport method since it is used by default.

So the refined snippet should look something like this:

$wp_customize->add_setting( 'posts_number_home' , array(
    'default'           => 10,
    'sanitize_callback' => 'absint',
) );

$wp_customize->add_control( 'posts_number_home', array(
    'label'    => __( 'Number of posts to display on homepage', 'mytheme' ), 
    'section'  => 'mytheme_options',
    'settings' => 'posts_number_home',
    'type'     => 'number',
    'priority' => 10,
    'input_attrs' => array(
        'min' => 1,
        'max' => 10
    )
) );

Edit 07/01/2016: Using intval is not correct because Customizer secretly passes the second object parameter to sanitization callback, while intval expects an optional integer. So the best way to sanitize non-negative integer is absint.

Answer 2

Think I figured it out. Type number definitely works not allowing text input. And it includes little arrow counters for the user. And you can add min max attributes. Someone let me know if this is incorrect in any way, particularly the sanitization.

$wp_customize->add_setting( 'posts_number_home' , array(
'default'     => '10',
'transport'   => 'refresh',
'sanitize_callback' => 'sanitize_text_field',
) );

$wp_customize->add_control( new WP_Customize_Control( 
$wp_customize, 
'posts_number_home',
array(
    'label'    => __( 'Number of posts to display on homepage', 'mytheme' ), 
    'section'  => 'mytheme_options',
    'settings' => 'posts_number_home',
    'type' => 'number',
    'priority' => 10,
    'input_attrs' => array(
    'min'   => 1,
    'max'   => 10,)
) 
));