Aggregate Number of High CPU alerts from Nagios Logs

Aggregate.php

#grep the logs like this
#grep "SERVICE ALERT: <instanceid>;Load;.* : CRITICAL" /var/log/nagios3/archives/nagios-* > critical_load.txt
<?php
$file = file('~/critical_load.txt');
#initialise empty hashmap
$map = array();
$hours = array();
foreach($file as $line){
    #read timestamp
    $guffpos = strpos($line,'[')+1;
    $timestamp = substr($line,$guffpos,10);
    #make a hour minute string "H:i"
    $hr = date('H:',$timestamp);
    $min = date(':i',$timestamp);
    #increment count in hashmap of "H:i"
    if(isset($map[$hr])){
        $map[$hr]=$map[$hr].$min." ";
    }else{
        $map[$hr]=$min." ";
    }
}
#print hashmap (nicely)
$i=0;
$keys = array_keys($map);
echo "Aggregated Load Errors by hour:".PHP_EOL;
echo "Hour"." "."NumErrors".PHP_EOL;
foreach($map as $str){
    $count = strlen($str)/4;
    echo $keys[$i]." ".$count.PHP_EOL;
    $i++;
}