Update element in xml file via php

I have generated xml file and I need within php select xml file, delete some values (<typ:numberRequested>22SP00001</typ:numberRequested>) and update all elements (<pri:rateVAT>none</pri:rateVAT>), (typ:unitPrice>2.82</typ:unitPrice><typ:price>2.82</typ:price> <typ:priceVAT>0</typ:priceVAT><typ:priceSum>2.82</typ:priceSum>) updating from mysql database by element <pri:code>1045</pri:code>.
Also I need delete <pri:homeCurrency> in pri:prijemkaSummary.
So I need select file, update/delete values and save is as another file.
I prefer procedural programing.