php variable $_SERVER['SERVER_ADDR'] is blank when using crontab - php

Question

I have a small script which gets basic information like the server IP-, and the MAC-address of the server the script is running on, I am then posting the results to a mysql database, this works fine and the code is shown below. However when I use a cronjob to execute the script everything but the IP address is being stored, for some reason the $_SERVER['SERVER_ADDR'] is blank when being executed as a cronjob.
This script runs every min, and is run on multi Raspberry PI's so I can tell which is connected to share job requests.
$mac_address = getMacLinux();
$server_ip = $config['server_ip'];
$client_ip = $_SERVER['SERVER_ADDR'];
$client_name = $config['client_name'];
$ch = curl_init();
$url = "{$server_ip}/checkin0.php";
echo "url = {$url}"."<br>";
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, "client_ip={$client_ip}&client_name={$client_name}&client_mac={$mac_address}");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$output = curl_exec ($ch); // Execute
curl_close ($ch); // Close cURL handle
var_dump($output); // Show output

Answer 1

i found the following
function getServerAddress() {
if(isset($_SERVER["SERVER_ADDR"]))
return $_SERVER["SERVER_ADDR"];
else {
// Running CLI
if(stristr(PHP_OS, 'WIN')) {
// Rather hacky way to handle windows servers
exec('ipconfig /all', $catch);
foreach($catch as $line) {
if(eregi('IP Address', $line)) {
// Have seen exec return "multi-line" content, so another hack.
if(count($lineCount = split(':', $line)) == 1) {
list($t, $ip) = split(':', $line);
$ip = trim($ip);
} else {
$parts = explode('IP Address', $line);
$parts = explode('Subnet Mask', $parts[1]);
$parts = explode(': ', $parts[0]);
$ip = trim($parts[1]);
}
if(ip2long($ip > 0)) {
echo 'IP is '.$ip."\n";
return $ip;
} else
; // TODO: Handle this failure condition.
}
}
} else {
$ifconfig = shell_exec('/sbin/ifconfig eth0');
preg_match('/addr:([\d\.]+)/', $ifconfig, $match);
return $match[1];
}

Answer 2

Look in the manual
$_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server
PS. Also you can use your script as CGI script (and $_SERVER['SERVER_ADDRESS'] will be correct). You may try fetch, wget, curl... and call script from crontab i.e. (server-IP is 192.168.0.1):
1 * * * * fetch http://192.168.0.1/my_script.php