WordPress Random Testimonial Shortcode

random-testimonial.php

<?php
//[random_testimonial]
function random_testimonial_func( $atts ){ 
    $query = new WP_Query( array ( 'category__in' => array( 4 ), 'posts_per_page' => -1, 'ignore_sticky_posts' => 1, ) );
    $testimonials = array();
    while( $query->have_posts() ) : $query->the_post();
      
        $testimonials[] = get_the_content();    
    
    endwhile;   

    $picked = array_rand($testimonials, 1);    
    
    return apply_filters('the_content', $testimonials[$picked]);
}
add_shortcode( 'random_testimonial', 'random_testimonial_func' );