filelogger.php

См. документацию.

<?php

 
namespace Bitrix\Main\Diag;
 
class FileLogger extends Logger
{
    protected $fileName;
    protected $maxSize = 1048576;

    public function __construct(string $fileName, int $maxSize = null)
    {
        $this->fileName = $fileName;
 
        if ($maxSize !== null)
        {
            $this->maxSize = $maxSize;
        }
    }
 
    protected function logMessage(string $level, string $message)
    {
        $current = ignore_user_abort(true);
 
        if ($fp = fopen($this->fileName, 'ab'))
        {
            if (flock($fp, LOCK_EX))
            {
                if ($this->maxSize > 0)
                {
                    // need it for filesize()
                    clearstatcache();
                    $logSize = filesize($this->fileName);
 
                    if ($logSize > $this->maxSize)
                    {
                        $this->rotateLog();
                        ftruncate($fp, 0);
                    }
                }
 
                fwrite($fp, $message);
                fflush($fp);
                flock($fp, LOCK_UN);
            }
            fclose($fp);
        }
 
        ignore_user_abort($current);
    }
 
    protected function rotateLog()
    {
        $historyName = $this->fileName . '.old';
 
        copy($this->fileName, $historyName);
    }
}