PHP Cookbook

17.10. Checking if a Host Is Alive

Problem

You want to ping a host to see if it is still up and accessible from your location.

Solution

Use PEAR’s Net_Ping package:

require 'Net/Ping.php';

$ping = new Net_Ping;
if ($ping->checkhost('www.oreilly.com')) {
    print 'Reachable';
} else {
    print 'Unreachable';
}

$data = $ping->ping('www.oreilly.com');

Discussion

The ping program tries to send a message from your machine to another. If everything goes well, you get a series of statistics chronicling the transaction. An error means that ping can’t reach the host for some reason.

On error, Net_Ping::checkhost( ) returns false, and Net_Ping::ping( ) returns the constant PING_HOST_NOT_FOUND. If there’s a problem running the ping program (because Net_Ping is really just a wrapper for the program), PING_FAILED is returned.

If everything is okay, you receive an array similar to this:

$results = $ping->ping('www.oreilly.com');

foreach($results as $result) { print "$result\n"; }
PING www.oreilly.com (209.204.146.22) from 192.168.123.101 : 
                   32(60) bytes of data.
               40 bytes from www.oreilly.com (209.204.146.22): icmp_seq=0 ttl=239 
                   time=96.704 msec
               40 bytes from www.oreilly.com (209.204.146.22): icmp_seq=1 ttl=239
                   time=86.567 msec
               40 bytes from www.oreilly.com (209.204.146.22): icmp_seq=2 ttl=239
                   time=86.563 msec
               40 bytes from www.oreilly.com (209.204.146.22): icmp_seq=3 ttl=239
                   time=136.565 msec
               40 bytes from www.oreilly.com (209.204.146.22): icmp_seq=4 ttl=239
                   time=86.627 msec

                -- - www.oreilly.com ping ...