<?php

$propertyName = "snake_case_property";

$search = ['/^[a-z]/e','/_[a-z]/e','/_/'];
$replace = ['strtoupper("$0")','strtoupper("$0")', ''];

$getter = 'get' . preg_replace($search, $replace, $propertyName);
$setter = 'set' . preg_replace($search, $replace, $propertyName);