pewc_default_field_value.php

<?php
/**
 * Automatically populate a field with user data
 * Enter the user field in the 'Default' field
 * Wrapped in {}
 * E.g. {first_name}
 */ 
function junhee_populate_user_field( $value, $id, $item, $posted ) {
	
	if( is_user_logged_in() ) {
		
		// Check if the default value is wrapped in {}
		if( substr( $value, 0, 1) == '{' ) {
			$stripped_value = str_replace( array( '{', '}' ), '', $value );
			$user_id = get_current_user_id();
			$value = get_user_meta( $user_id, $stripped_value, true );
		}

	}
	
	return $value;
  
}
add_filter( 'pewc_default_field_value', 'junhee_populate_user_field', 10, 4 );