How to add or remove body classes in WordPress

WP_add_remove_body_class.php

<?php

// WP Add Remove Body Classes

// Add
add_filter( 'body_class','mh_body_classes' );
function my_body_classes( $classes ) {
  $classes[] = 'class-name';
  $classes[] = 'class-name-two';

  if ( is_page_template( 'page-tempate_name.php' ) ) {
    $classes[] = 'class-name-three';
  }

  return $classes;
}

// Remove
add_filter('body_class', function (array $classes) {
  if (in_array('class-to-remove', $classes)) {
    unset( $classes[array_search('class-to-remove', $classes)] );
  }
  return $classes;
});


// Remove
function mh_remove_body_class($classes, $class) {
  foreach ( $classes as $key => $value ) {
    if ( $value == 'error404' ) unset( $classes[ $key ] );
  }
  return $classes;
}
add_filter( 'body_class', 'st_remove_body_class', 10, 2 );