Get age WordPress shortcode with birthdate parameter

functions.php

/*
* Get the age automatically with the given birth date.
*/

function getAge( $atts = [] ) {
    
    $atts = array_change_key_case( (array) $atts, CASE_LOWER );

    $age_atts = shortcode_atts(
        array(
            'birthdate' => 'January 1, 1970',
        ), $atts
    );

    	/* Based on David Miles code: https://www.facebook.com/groups/916625091796611 */
	
	$age = date_diff(date_create($age_atts['birthdate']), date_create('now'))->y;
	
    return $age;
}
 
function getAge_init() {
    add_shortcode( 'get-age', 'getAge' );
}
 
add_action( 'init', 'getAge_init' );

// Put the shortcode like this on the text editor: [get-age birthdate="January 01, 1970"]