Run PHP file when external file is updated

[davefootball123]

I coded a PHP script that sends a text message to a list of people who are subscribed when severe weather warnings are issued. The script works good. However the problem right now is if I have it on a cron job every 5 minutes to check for a warning, every 5 minutes that a warning is in effect a text message will be sent to the subscribers. Is there a way to have a 5 minutes cron job but only send the text if the external file at the weather service is updated? That probably sounds really complicated but I will include my simple part of the text message script. Thanks for the help, Dave

 

<?PHP
//SUBJECT AND BODY OF EMAIL SHOULD BE LESS THAN 160 CHARACTERS TOTAL
$url = 'http://www.weatheroffice.gc.ca/rss/warning/on-151_e.xml';
$search_torwarn = 'SNOW SQUALL WARNING IN EFFECT';
$subject = "SOWX ALERT";
$message = "Snow Squall Warning For: Barrie - Collingwood - Hillsdale. Visit http://www.sowx.ca for more information. ";

$file_contents = file_get_contents($url);


if(strpos($file_contents, $search_torwarn) !== FALSE){

mail("@msg.telus.com,6@msg.telus.com",$subject,$message,"From: SOWX ALERTS");

}

?>

Edited February 3, 2013 by davefootball123

[requinix]

Store the time of the most recent alert somewhere, like a database, then only send the message if there's anything newer.

[davefootball123]

Would looking at the time of the bulletin work? And how would you go about comparing the time to the bulletin?

[davefootball123]

OK I noticed something http://www.weatheroffice.gc.ca/rss/warning/on-151_e.xml the xml has a publish date/time. Could you compare that to current time and say if time is < 2 minutes then send a text.

[requinix]

>5 minutes ago, yes. It's not as foolproof as storing the time from the last alert but it'll probably be good enough.

[davefootball123]

Could the time of the last alert be stored in a text file?

[trq]

If you have sufficient access to install software on this system you could use incron instead of a regular cron daemon.

 

incron runs tasks based on filesystem events. This allows you to execute a script when a file changes for instance.

[davefootball123]

I think what im going to do is read the xml issuance time. I will have a script read the xml for issuance of the warning. And if its new it will trigger the text message script. Do you think that would work?

[davefootball123]

I managed to get the creation time/update time of the bulletin and but it in a text file. That works good. Considering I only need it for the one file the next step may be easy. How can I have the script look at the text file with the time of the bulletin and have it only run the text script if the bulletin is new? Any Ideas or help would be greatly appreciated.

 

 

Thanks, Dave