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17.11. Checking if a Host Is Alive

17.11.3. 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 ( from : 
    32(60) bytes of data.
40 bytes from www.oreilly.com ( icmp_seq=0 ttl=239 
    time=96.704 msec
40 bytes from www.oreilly.com ( icmp_seq=1 ttl=239
    time=86.567 msec
40 bytes from www.oreilly.com ( icmp_seq=2 ttl=239
    time=86.563 msec
40 bytes from www.oreilly.com ( icmp_seq=3 ttl=239
    time=136.565 msec
40 bytes from www.oreilly.com ( icmp_seq=4 ttl=239
    time=86.627 msec

 -- - www.oreilly.com ping statistics  -- -
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/mdev = 86.563/98.605/136.565/19.381 ms

Net_Ping doesn't do any parsing of the data to pull apart the information, such as the packet loss percentage or the average round-trip time. However, you can parse it yourself:

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

// grab last line of array; equivalent to non-destructive array_pop( )
// or $results[count($results) - 1]
$round_trip = end($results);
preg_match_all('#[ /]([.\d]+)#', $round_trip, $times);

// pull out the data 
list($min,$avg,$max,$mdev) = $times[1];
// or print it out 
foreach($times[1] as $time) { print "$time\n"; }

This regular expression searches for either a space or a slash. It then captures a sequence of one or more numbers and a decimal point. To avoid escaping /, we use the # nonstandard character as your delimiter.

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