woocommerce_admin_product_custom_fields.php

<?php

// Display product Fields
add_action( 'woocommerce_product_options_general_product_data', 'ci_custom_general_tab_fields' );

function ci_custom_general_tab_fields() {
  global $woocommerce, $post;
  
  echo '<div class="options_group">';
  
  // Text Field
woocommerce_wp_text_input( 
	array( 
		'id'          => '_text_field', 
		'label'       => __( 'Text Field', 'woocommerce' ), 
		'placeholder' => '',
		'desc_tip'    => 'true',
		'description' => __( 'Enter text here.', 'woocommerce' ) 
	)
);
// Number Field
woocommerce_wp_text_input( 
	array( 
		'id'                => '_number_field', 
		'label'             => __( 'Number Field', 'woocommerce' ), 
		'placeholder'       => '', 
        'desc_tip'    => 'true',
		'description'       => __( 'Enter number here.', 'woocommerce' ),
		'type'              => 'number', 
		'custom_attributes' => array(
				'step' 	=> 'any',
				'min'	=> '0'
			) 
	)
);
// Textarea
woocommerce_wp_textarea_input( 
	array( 
		'id'          => '_textarea', 
		'label'       => __( 'Textarea Field', 'woocommerce' ), 
		'placeholder' => '', 
        'desc_tip'    => 'true',
		'description' => __( 'Enter custom detail here.', 'woocommerce' ) 
	)
);
// Select
woocommerce_wp_select( 
array( 
	'id'      => '_select', 
	'label'   => __( 'Select Field', 'woocommerce' ), 
	'options' => array(
		'one'   => __( 'Option 1', 'woocommerce' ),
		'two'   => __( 'Option 2', 'woocommerce' ),
		'three' => __( 'Option 3', 'woocommerce' )
		)
	)
);
// Checkbox
woocommerce_wp_checkbox( 
array( 
	'id'            => '_checkbox', 
	'wrapper_class' => 'show_if_simple', 
	'label'         => __('Checkbox Field', 'woocommerce' ), 
	'description'   => __( 'Check me!', 'woocommerce' ) 
	)
);
// Hidden field
woocommerce_wp_hidden_input(
array( 
	'id'    => '_hidden_field', 
	'value' => 'hidden_value'
	)
);
// Custom field Type
?>
<p class="form-field custom_field_type">
	<label for="custom_field_type"><?php echo __( 'Custom Field 1', 'woocommerce' ); ?></label>
	<span class="wrap">
		<?php $custom_field_one = get_post_meta( $post->ID, '_custom_field_one', true ); ?>	
		<input placeholder="<?php _e( 'Field One', 'woocommerce' ); ?>" class="" type="number" name="_field_one" value="<?php echo $custom_field_one; ?>" step="any" min="0"  />
	</span>
	<span class="description"><?php _e( 'Place description here!', 'woocommerce' ); ?></span>
</p>


<p class="form-field custom_field_type">
	<label for="custom_field_type"><?php echo __( 'Custom Field 2', 'woocommerce' ); ?></label>
	<span class="wrap">
		<?php $custom_field_two = get_post_meta( $post->ID, '_custom_field_two', true ); ?>	
		<input placeholder="<?php _e( 'Field Two', 'woocommerce' ); ?>" type="date" name="_field_two" value="<?php echo $custom_field_two; ?>" step="any" />
	</span>

</p>



<!-- product select -->

<p class="form-field product_field_type">
<label for="product_field_type"><?php _e( 'Woo Product Select', 'woocommerce' ); ?></label>
<select id="product_field_type" name="product_field_type[]" class="wc-enhanced-select" multiple="multiple" data-placeholder="<?php _e( 'Search for a product&hellip;', 'woocommerce' ); ?>">
	<?php
	
 $query = new WC_Product_Query( array(
    'limit' => 7,
    'orderby' => 'date',
    'order' => 'DESC',
    'return' => 'ids',
) );
$product_ids = $query->get_products();  
       
		if ( $product_ids ) {
		  
          $i=0;
			foreach ( $product_ids as $product_id ) {
				
                $product      = get_product( $product_id );
				$product_name = woocommerce_get_formatted_product_name( $product );
                
                
                $product_field_type_ids = get_post_meta( $post->ID, '_product_field_type_ids', true );
                $prod_ids = ! empty( $product_field_type_ids ) ? array_map( 'absint',  $product_field_type_ids ) : null;
                
                
                if($product_id == $prod_ids[$i])
                {
                   echo '<option value="' . esc_attr( $product_id ) . '" selected="selected">' . esc_html( $product_name ) . '</option>';
                         
                       
                }
                else
                {
                    echo '<option value="' . esc_attr( $product_id ) . ' ">' . esc_html( $product_name ) . '</option>';
                }
                
                $i++;
                    
                
			}
            
            
		}
	?>
</select> <img class="help_tip" data-tip='<?php _e( 'Your description here', 'woocommerce' ) ?>' src="<?php echo $woocommerce->plugin_url(); ?>/assets/images/help.png" height="16" width="16" />
</p>
<?php
  
  echo '</div>';
	
}