Function to get current CPU load as percentage value under Windows and Linux.

Note: Function is getServerLoad(). It will return a decimal value as percentage of current CPU load or NULL if something went wrong (e. g. insufficient access rights).

<?php

    header("Content-Type: text/plain");

    function _getServerLoadLinuxData()
    {
        if (is_readable("/proc/stat"))
        {
            $stats = @file_get_contents("/proc/stat");

            if ($stats !== false)
            {
                // Remove double spaces to make it easier to extract values with explode()
                $stats = preg_replace("/[[:blank:]]+/", " ", $stats);

                // Separate lines
                $stats = str_replace(array("\r\n", "\n\r", "\r"), "\n", $stats);
                $stats = explode("\n", $stats);

                // Separate values and find line for main CPU load
                foreach ($stats as $statLine)
                {
                    $statLineData = explode(" ", trim($statLine));

                    // Found!
                    if
                    (
                        (count($statLineData) >= 5) &&
                        ($statLineData[0] == "cpu")
                    )
                    {
                        return array(
                            $statLineData[1],
                            $statLineData[2],
                            $statLineData[3],
                            $statLineData[4],
                        );
                    }
                }
            }
        }

        return null;
    }

    // Returns server load in percent (just number, without percent sign)
    function getServerLoad()
    {
        $load = null;

        if (stristr(PHP_OS, "win"))
        {
            $cmd = "wmic cpu get loadpercentage /all";
            @exec($cmd, $output);

            if ($output)
            {
                foreach ($output as $line)
                {
                    if ($line && preg_match("/^[0-9]+\$/", $line))
                    {
                        $load = $line;
                        break;
                    }
                }
            }
        }
        else
        {
            if (is_readable("/proc/stat"))
            {
                // Collect 2 samples - each with 1 second period
                // See: https://de.wikipedia.org/wiki/Load#Der_Load_Average_auf_Unix-Systemen
                $statData1 = _getServerLoadLinuxData();
                sleep(1);
                $statData2 = _getServerLoadLinuxData();

                if
                (
                    (!is_null($statData1)) &&
                    (!is_null($statData2))
                )
                {
                    // Get difference
                    $statData2[0] -= $statData1[0];
                    $statData2[1] -= $statData1[1];
                    $statData2[2] -= $statData1[2];
                    $statData2[3] -= $statData1[3];

                    // Sum up the 4 values for User, Nice, System and Idle and calculate
                    // the percentage of idle time (which is part of the 4 values!)
                    $cpuTime = $statData2[0] + $statData2[1] + $statData2[2] + $statData2[3];

                    // Invert percentage to get CPU time, not idle time
                    $load = 100 - ($statData2[3] * 100 / $cpuTime);
                }
            }
        }

        return $load;
    }

    //----------------------------

    $cpuLoad = getServerLoad();
    if (is_null($cpuLoad)) {
        echo "CPU load not estimateable (maybe too old Windows or missing rights at Linux or Windows)";
    }
    else {
        echo $cpuLoad . "%";
    }

?>

Here is another one that also works on windows. Note that this method is not fast, so be careful in the number of calls to this function.

<?php
function get_server_load() {
    
        if (stristr(PHP_OS, 'win')) {
        
            $wmi = new COM("Winmgmts://");
            $server = $wmi->execquery("SELECT LoadPercentage FROM Win32_Processor");
            
            $cpu_num = 0;
            $load_total = 0;
            
            foreach($server as $cpu){
                $cpu_num++;
                $load_total += $cpu->loadpercentage;
            }
            
            $load = round($load_total/$cpu_num);
            
        } else {
        
            $sys_load = sys_getloadavg();
            $load = $sys_load[0];
        
        }
        
        return (int) $load;
    
    }
?>

It is important to note that sys_getloadavg() does not return a percentage, and the numbers that it returns are completely meaningless if you do not know the number of CPU cores. To get the number as a percentage you need to divide the value by the number of CPU cores in the system. (eg: if the value is 0.5 and you have two cores, then you are using 25% of the CPU on average). Here is a simple function to get the values as a percent:

<?php
function percentloadavg(){
    $cpu_count = 1;
    if(is_file('/proc/cpuinfo')) {
        $cpuinfo = file_get_contents('/proc/cpuinfo');
        preg_match_all('/^processor/m', $cpuinfo, $matches);
        $cpu_count = count($matches[0]);
    }

    $sys_getloadavg = sys_getloadavg();
    $sys_getloadavg[0] = $sys_getloadavg[0] / $cpu_count;
    $sys_getloadavg[1] = $sys_getloadavg[1] / $cpu_count;
    $sys_getloadavg[2] = $sys_getloadavg[2] / $cpu_count;

    return $sys_getloadavg;
}
?>

I was having a problem with a large script I need to run - was a loop through about 50,000 records and downloading several pictures for a bunch of them, and updating the database.

the problem came as I started getting visitors to my site, the server would get behind, run out of memory, iowait skyrockets, mysql slows down... was a total downhill spiral.

Use this to fix it.

$load = sys_getloadavg();
$sleep=5;
$maxload=2;
if ($load[0] > $maxload) {
       sleep($sleep);
    echo "Busy server - sleep $sleep seconds<br>";
}

I have to play with the load and the sleep number to find what worked for my script, but now my server does not bog at all.

the codes below will provide this function for order versions of PHP.
if (!function_exists('sys_getloadavg')) {
    function sys_getloadavg()
    {
        $loadavg_file = '/proc/loadavg';
        if (file_exists($loadavg_file)) {
            return explode(chr(32),file_get_contents($loadavg_file));
        }
        return array(0,0,0);
    }
}

To get just current load avg, you can do :

<?php
$output = shell_exec('cat /proc/loadavg');
$loadavg = substr($output,0,strpos($output," "));
?>

The code below mimics the output of sys_getloadavg(). You may have to tweak the way the substring is captured for different distros.

<?php

function sys_getloadavg_hack()
{
    $str = substr(strrchr(shell_exec("uptime"),":"),1);
    $avs = array_map("trim",explode(",",$str));

    return $avs;
}

print_r(sys_getloadavg_hack());

// Array
// (
//     [0] => 6.24
//     [1] => 4.92
//     [2] => 3.99
// )

?>

This function is a neat way of running low priority or non-essential cron jobs on a busy server - if the load is high, don't continue with the task (and try again in a few minutes time).

Use this:
<?php
$loads=sys_getloadavg();
$core_nums=trim(shell_exec("grep -P '^physical id' /proc/cpuinfo|wc -l"));
$load=$loads[0]/$core_nums;
echo $load;
?>

equivalent for windows
<?php
ob_start();
passthru('typeperf -sc 1 "\processor(_total)\% processor time"',$status);
$content = ob_get_contents();
ob_end_clean();
if ($status === 0) {
    if (preg_match("/\,\"([0-9]+\.[0-9]+)\"/",$content,$load)) {
        if ($load[1] > get_config('busy_error')) {
            header('HTTP/1.1 503 Too busy, try again later');
            die('Server too busy. Please try again later.');
        }
    }
}
?>

// To get correct number of CPU cores
// as to calculate correct usage

function getCpuCores() {
    // Linux
    if (stristr(PHP_OS, 'linux')) {
        // First, try /proc/cpuinfo
        if (file_exists('/proc/cpuinfo')) {
            preg_match_all('/^processor/m', file_get_contents('/proc/cpuinfo'), $matches);
            if ($matches[0]) return count($matches[0]);
        }
        // Fallback: Use nproc command
        return (int)shell_exec('nproc');
    }

    // macOS
    if (stristr(PHP_OS, 'darwin')) {
        return (int)shell_exec('sysctl -n hw.physicalcpu');
    }

    // Windows
    if (stristr(PHP_OS, 'win')) {
        // Try wmic command first
        $cpuCount = shell_exec('wmic cpu get NumberOfLogicalProcessors');
        if ($cpuCount) {
            preg_match('/\d+/', $cpuCount, $matches);
            if (isset($matches[0])) return (int)$matches[0];
        }
        // Fallback: Use environment variable
        return (int)getenv('NUMBER_OF_PROCESSORS');
    }

    // If failed
    return false;
}

// Example usage
// get CPU cores
$cores = getCpuCores();

if (is_Numeric($cores)) {
    $corePerc = 100/$cores;
} else {
    $corePerc = 100;
    $cores = 'Unknown';
}
echo '<div><b>CPU:</b> '.$cores .' cores</div>';

// show correct CPU usage
echo '<blockquote>';
$cpu = sys_getloadavg();
echo(round($cpu[0]*$corePerc) .'% - last min<br>');
echo(round($cpu[1]*$corePerc) .'% - last 5 mins<br>');
echo(round($cpu[2]*$corePerc) .'% - last 15 mins<br>');
echo '</blockquote>';

simple function to get the cpu load with availability to most os platforms because I haven't actually been able to find a similar protocol if you happen to be testing out various os platforms...

function cpu_load():?string {
    $load='';
    if(strtolower(PHP_OS_FAMILY)=="windows") {
        exec("wmic cpu get loadpercentage /all",$out);
        if($out) {
            foreach($out as $line) {
                if($line&&preg_match("/^[0-9]+\$/",$line)) {
                    $load=$line;
                    break;
                }
            }
        }
    } else {
        $load=sys_getloadavg();
    }
    return $load;
}

<?php // Usage processor in Windows using FFI
  if(!dl("ffi")) // Load the extension
    throw new Exception('Cound not load the FFI extension.');

  function GetSystemTimes()
  {
    static $Kernel32;
    $Kernel32??=FFI::cdef(<<<'IDL'
      bool GetSystemTimes(long long *IdleTime, long long *KernelTime, long long *UserTime);
      int GetLastError();
    IDL, 'Kernel32.dll');
    
    $IdleTime   = FFI::new('long long');
    $KernelTime = FFI::new('long long'); // already has idle time
    $UserTime   = FFI::new('long long');
  
    if($Kernel32->GetSystemTimes(FFI::addr($IdleTime), FFI::addr($KernelTime), FFI::addr($UserTime)))
      return [
        'Idle'   =>$IdleTime   ->cdata,
        'Kernel' =>$KernelTime ->cdata, // already has idle time
        'User'   =>$UserTime   ->cdata,
      ];
    return [];
  }
  
  function GetSystemTimesDelta()
  {
    static $Last=null;
    static $Delta=[0,1];
    $Times=GetSystemTimes();
    $Last??=$Times;
    $Idle =$Times['Idle'   ]-$Last['Idle'   ];
    $All  =$Times['Kernel' ]-$Last['Kernel' ]+  // Kernel already has idle time
           $Times['User'   ]-$Last['User'   ];
    if($All>1_000_000) // 100ms
    {
      $Delta=[$Idle, $All];
      $Last=$Times;
    }
    return $Delta;
  }

  function ProcessorLoad()
  {
    static $Load=0;
    [$Idle, $All]=GetSystemTimesDelta();
    if($All>0.0)
      $Load=1-$Idle/$All;
    return $Load;
  }
  
  function KbHit()
  {
    Static $Sys;
    $Sys??=FFI::cdef('bool _kbhit();', 'msvcrt.dll');
    return $Sys->_kbhit();
  }
  
  while(!KbHit())
  {
    echo str_pad((string)round(ProcessorLoad()*100), 3, ' ', STR_PAD_LEFT), "%\n";
    sleep(1);
  }
?>

You can emulate loadavg using this. Can also be used to get iowait

<?php
   function ProcStats()
   {    
       $fp=fopen("/proc/stat","r");
       if(false===$fp)
               return false;
       $a=explode(' ',fgets($fp));
       array_shift($a); //get rid of 'cpu'
       while(!$a[0])
           array_shift($a); //get rid of ' '
       var_dump($a);
       fclose($fp);
       return $a;
   }

   $a=ProcStats();
   sleep(5);
   $b=ProcStats();

   
   $total=array_sum($b)-array_sum($a);
   
   $loadavg = round(100* (($b[0]+$b[1]+$b[2]) - ($a[0]+$a[1]+$a[2])) / $total, 2); // user+nice+system
   $iowait= round(100* ($b[4] - $a[4])/$total,2);

?>