Grazie mille per il suggerimento.
Ho provato echo file_get_contents($apicall) e mi visualizza questo:

2008-11-16T11:08:03.224Z Success e591_core_Bundled_7560815_R1 591 270303330486 true 15.99 2008-11-16T11:08:32.000Z http://cgi.ebay.com/Belkin-Sports-Ar...QQcmdZViewItem Chinese http://thumbs1.ebaystatic.com/pict/2...04868080_1.jpg 20336 Cell Phones & PDAs:Cell Phone & PDA Accessories 0 9.99 Active PT29S 0.0 Flat 260315333715 2008-11-16T11:08:44.000Z http://cgi.ebay.com/OZ-Crystal-Case-...QQcmdZViewItem FixedPriceItem http://thumbs1.ebaystatic.com/pict/2...37158080_1.jpg 161656 Phones:Mobile Accessories:Cases:Apple iPhone 1.05 Active PT41S 5.1 Flat 160298463162 2008-11-16T11:09:00.000Z http://cgi.ebay.com/Silicon-Case-Pro...QQcmdZViewItem FixedPriceItem http://thumbs1.ebaystatic.com/pict/1...31628080_1.jpg 20336 Cell Phones & PDAs:Cell Phone & PDA Accessories 3.68 Active PT57S 0.0 Flat 67838 http://search.ebay.com/ws/search/Sal...satitle=iphone

Mi servirebbe salvare il tutto in un file XML. Come posso fare?