php code to upload a url correctly

I have a form in which users submit a url. I am having problems as some people submit the url in the format http://www.blah.blah.org <http://www.blah.blah.org/> while others submit in the format www.blah.blah.org <http://www.blah.blah.org/> I have designed the form so that it seems fairly obvious (to me anyway) not to include the http:// but people are still doing it (presumably because they are copying and pasting from a browser). My form processing script is designed to add http:// to the submitted url and place the modified url in a database for future use. As you can imagine sometimes I end up with urls such as http://http://www.blah.blah.org <http://http:/www.blah.blah.org> in my database. Hence I need a more rigorous form processing script that is capable of first checking if the url includes http:// and then processes accordingly. Can anyone point me in the right direction for such a script? Thanks Dr James Corden Technology Evaluation Manager TrusTECH, Innovation Unit 1st Floor Postgraduate Centre Manchester Royal Infirmary Oxford Road Manchester M13 9WL Tel: 0161 276 5782 Fax: 0161 276 5766 E-mail: james.corden@cmmc.nhs.uk Web: http://www.trustech.org.uk This email and any files transmitted with it are confidential and solely for the use of the intended recipient. It may contain material protected by law as a legally privileged document and copyright work. Its content should not be disclosed and it should not be given or copied to anyone other than the person(s) named or referenced above. If you are not the intended recipient or the person responsible for delivering to the intended recipient, be advised that you have received this email in error and that any use is strictly prohibited. If you have received this email in error please notify sender immediately on +44 (0161) 276 5782