Well, I wrote that script quite a while ago, it worked for me, so here you are:
#!/usr/bin/php -q <?php $host = $argv[1]; $user = $argv[2]; $pass = $argv[3]; $link = mysql_connect ( $host, $user, $pass ); $result = mysql_query ( "SHOW SLAVE STATUS" ); $stat = mysql_fetch_assoc($result); mysql_free_result ( $result ); mysql_close ( $link ); if ( $stat['Seconds_Behind_Master'] < "10" && $stat['Last_Errno'] == "0" && $stat['Slave_IO_Running'] == "Yes" && $stat['Slave_SQL_Running'] == "Yes") { echo "OK Replication Host: " . $stat['Master_Host'] . " Seconds behind master: " . $stat['Seconds_Behind_Master'] . "s\n"; exit ( 0 ) ; } else if ( $stat['Seconds_Behind_Master'] > 20 && $stat['Seconds_Behind_Master'] < 100 && $stat['Last_Errno'] == "0" && $stat['Slave_IO_Running'] == "Yes" && $stat['Slave_SQL_Running'] == "Yes") { echo "WARNING Replication " . $stat['Master_Host'] . " Seconds behind master: " . $stat['Seconds_Behind_Master'] . "s\n"; exit ( 1 ); } else { echo "CRITICAL Replication " . $stat['Master_Host'] . " Seconds behind master: " . $stat['Seconds_Behind_Master'] . "s | Error: " . $stat['Last_Error'] . "\n"; exit ( 2 ); } ?>
Just put it in a file like /usr/local/nrpe/libexec/check_mysql_replication.php and run it with the correct parameters:
/usr/local/nrpe/libexec/check_mysql_replication.php SERVERHOST USERNAME PASSWORD
Done.