Re: Creating Unique Values

On Wed, 4 Oct 2000, Andy Woolley wrote: > Thanks Andrew, > > I decided to use the function called erm.... the one that I can never > remember what it's called without looking in the manual. > > microtime(); that's it. > > Heres what I did: > > $uniquevalue = microtime(); > $uniquevalue = ereg_replace ("\.", "", $uniquevalue); #get rid of the > period. > setcookie("cookieset", $uniquevalue); > > As microtime() takes it start time from the Unix Epoch (0:00:00 January 1, > 1970 GMT) the chances of a duplicate are......shall we say slim. The probability of a collision on your common UNIX system is 1/100, because the resolution of the timer is usually 100Hz. That almost guarantees problems, if your application relies on having unique ids. A better approach is to use PHP's uniqid() and to enable the lcg. Feed the result through md5 and the probability of a collision is reduced significantly. $id = md5(uniqid("mysite", 1)); - Sascha