php - set interval

hello, i've been searching for a 'setInterval' function in php and haven't had much luck. in actionscript (which is similar to php) you can make a function which calls another function at a set interval, and i was keen to do this with php for a mail script so that rather than sending 500 emails at once, i can send 10 emails every 10 seconds etc. i'm currently thinking i'll have to use flash to make the interval, but would rather keep it all in php. basically what i want to do is this. function SendMail($howManyToSend, $fromWhatIndex){ // gets the number of email addresses ($howManyToSend) // from the database, starting at index $fromWhatIndex // then sends them if(all emails sent, no more emails in DB){ return 'finished'; }else{ return 'keep them coming'; } } function IntervalCalled (){ // increment currentIndex $currentIndex = $currentIndex + 10; $howDidWeGo = SendMail(10, $currentIndex); if($howDidWeGo == "finished"){ // FLASH CLEARINTERVAL COMMAND clearInterval($makeEmailsInterval); } } // THIS IS HOW I WOULD CALL THE INTERVAL IN FLASH // (for every 10 seconds) $makeEmailsInterval = setInterval(IntervalCalled, 10000); so is this possible with PHP by using functions? anything involving complicated server stuff means i may as well setup flash to call the interval instead of PHP many thanks andrew