maddisondesigns/functions.php

@Yorlinq You can use the get_categories() function to get a list of all Categories. You'd then simply loop through them and add each one to your select field. There's examples at the bottom of the page, in the User Contributed Notes, that show you how you can loop through them.

See: https://developer.wordpress.org/reference/functions/get_categories/

Oke, I got all categories visible in a select field but when I update, nothing gets saved.....?

/*

• Add our Custom Field to all products
  */
  function yl_woo_add_main_category_field( $post_id ) {

  echo '

  ';

  // Get product categories
  $terms = get_terms( array('taxonomy' => 'product_cat') );
  $options = []; // Initializing

  // Loop through each wp_term object and set term names in an array
  foreach ($terms as $term) {
  $term_name = __( $term->name, 'woocommerce' );
  $options[$term_name] = $term_name;
  }

  // Select
  woocommerce_wp_select( array(
  'id' => '_main_category',
  'label' => __( 'Main category', 'yorlinq' ),
  'placeholder' => '',
  'desc_tip' => true,
  'description' => __( 'Select a category to display above the product title on shop page.', 'yorlinq' ),
  'options' => $options,
  'value' => get_post_meta( $post_id, '_main_category', true ),
  ) );

  echo '

  ';

}
// General Tab
//add_action( 'woocommerce_product_options_pricing', 'yl_woo_add_main_category_field' ); // After pricing fields
//add_action( 'woocommerce_product_options_downloads', 'yl_woo_add_main_category_field' ); // After downloadable file fields and only visible when it's a downloable product
//add_action( 'woocommerce_product_options_tax', 'yl_woo_add_main_category_field' ); // After tax fields
add_action( 'woocommerce_product_options_general_product_data', 'yl_woo_add_main_category_field', 2 ); // After all General default fields

// Inventory tab
//add_action( 'woocommerce_product_options_sku', 'yl_woo_add_main_category_field' ); // After SKU field
//add_action( 'woocommerce_product_options_stock', 'yl_woo_add_main_category_field' ); // After Manage Stock field
//add_action( 'woocommerce_product_options_stock_fields', 'yl_woo_add_main_category_field' ); // After Manage Stock field but only visible is checked
//add_action( 'woocommerce_product_options_stock_status', 'yl_woo_add_main_category_field' ); // After Stock Status field
//add_action( 'woocommerce_product_options_sold_individually', 'yl_woo_add_main_category_field' ); // After Sold Individually field
//add_action( 'woocommerce_product_options_inventory_product_data', 'yl_woo_add_main_category_field' ); // After all Inventory default fields

// Shipping tab
//add_action( 'woocommerce_product_options_dimensions', 'yl_woo_add_main_category_field' ); // After Dimensions field
//add_action( 'woocommerce_product_options_shipping', 'yl_woo_add_main_category_field' ); // After all Shipping default fields

// Linked Products tab
//add_action( 'woocommerce_product_options_related', 'yl_woo_add_main_category_field' ); // After all Linked Products default fields

// Attributes tab
//add_action( 'woocommerce_product_options_attributes', 'yl_woo_add_main_category_field' ); // After all Attributes default fields

// Advanced tab
//add_action( 'woocommerce_product_options_reviews', 'yl_woo_add_main_category_field' ); // After Enable Reviews field
//add_action( 'woocommerce_product_options_advanced', 'yl_woo_add_main_category_field' ); // After all Advanced default fields

/*

• Save our simple product fields
  */
  function yl_woo_add_main_category_field_save( $post_id ){

  // Select
  $woocommerce_select = $_POST['_main_category'];
  update_post_meta( $post_id, '_main_category', esc_attr( $woocommerce_select ) );

}
add_action( 'woocommerce_process_product_meta', 'yl_woo_add_main_category_field_save' );

just had to remove 1 line: 'value' => get_post_meta( $post_id, '_main_category', true ),

And now it works :)

@maddisondesigns Hi Thank you very much for your code, it's beneficial to understand how to add custom fields for WC, and Thank you again.
Actually, I need to get variable data to display on single product page like this
/*

• Add our Custom Fields to variable products
  */
  function mytheme_woo_add_custom_variation_fields( $loop, $variation_data, $variation ) {

  echo '

  ';

  // Text Field
  woocommerce_wp_text_input(
  array(
  'id' => '_variable_text_field[' . $variation->ID . ']',
  'label' => __( 'My Text Field', 'woocommerce' ),
  'placeholder' => 'http://',
  'desc_tip' => true,
  'description' => __( "Here's some really helpful tooltip text.", "woocommerce" ),
  'value' => get_post_meta( $variation->ID, '_variable_text_field', true )
  )
  );

  // Add extra custom fields here as necessary...
  ?>

  ID, '_variable_custom_field_type', true ); ?>

  echo '
  ';

}
// Variations tab
//add_action( 'woocommerce_variation_options', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After variation Enabled/Downloadable/Virtual/Manage Stock checkboxes
//add_action( 'woocommerce_variation_options_pricing', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After Price fields
//add_action( 'woocommerce_variation_options_inventory', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After Manage Stock fields
//add_action( 'woocommerce_variation_options_dimensions', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After Weight/Dimension fields
//add_action( 'woocommerce_variation_options_tax', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After Shipping/Tax Class fields
//add_action( 'woocommerce_variation_options_download', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After Download fields
add_action( 'woocommerce_product_after_variable_attributes', 'mytheme_woo_add_custom_variation_fields', 10, 3 ); // After all Variation fields

/*

• Save our variable product fields
  */
  function mytheme_woo_add_custom_variation_fields_save( $post_id ){

  // Text Field
  $woocommerce_text_field = $_POST['_variable_text_field'][ $post_id ];
  update_post_meta( $post_id, '_variable_text_field', esc_attr( $woocommerce_text_field ) );

  $variable_custom_field_type = array( esc_attr( $_POST['_field_one'] ), esc_attr( $_POST['_field_two'] ) );
  update_post_meta( $post_id, '_variable_custom_field_type', $variable_custom_field_type );

}
add_action( 'woocommerce_save_product_variation', 'mytheme_woo_add_custom_variation_fields_save', 10, 2 );

/*

• Display our example custom field above the summary on the Single Product Page
  */
  function mytheme_display_woo_custom_fields() {
  global $post;

  $ourTextField = get_post_meta( $post->ID, '_variable_text_field', true );

  if ( !empty( $ourTextField ) ) {
  echo '

  Download Report
  ';
  }
  }
  add_action( 'woocommerce_single_product_summary', 'mytheme_display_woo_custom_fields', 15 );
  I added a text field to the variable product and added a file URL to the text field. this process correctly works in the simple product, but variable products did not show correctly. how can I get correctly variable data to here( <a href="' . $ourTextField . '">Download Report</a> ).but all variable data save correctly in DB. @maddisondesigns can you please help me to fix this
  Thank you