Top command with php does not return the same terminal value

Question

Well I am building a php code to monitor my CPU usage. I am using the top command that is native to linux. I am using a pc with Ubuntu server 18.04 for testing.

Well what happens is that I open the terminal and run php together, the value of the cpu is always higher in the terminal, which is around 20% on average and php is locked in 9.1%.

I’m going to post the code I’m putting together, I wanted to know the reason for the difference and how to fix it.

    // Executa comando para consulta da CPU
exec('top -d 0 -n 5 -b | grep Cpu', $cpu);
preg_match('/\d+\../', $cpu[0], $cpu_us);

// Monta array com os cores do processador
for($i=1; $i < count($cpu);$i++){
    preg_match('/\d+\../', $cpu[$i], $cores_us);
    $cores[] = $cores_us[0];
}



// Monta o array de resposta
$array = array(
    "cpu" => array(
        "geral" => $cpu_us[0],
        "cores" => $cores
    )
);

var_dump($array);

OBS: I realized that whenever I run php the values of the colors are changing, but the general cpu does not change much.