<?php declare(strict_types=1);

/*
 * This file is part of the Monolog package.
 *
 * (c) Jordi Boggiano <j.boggiano@seld.be>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Monolog\Processor;

/**
 * Adds a unique identifier into records
 *
 * @author Simon Mönch <sm@webfactory.de>
 */
class UidProcessor
{
    private $uid;

    public function __construct(int $length = 7)
    {
        if (!is_int($length) || $length > 32 || $length < 1) {
            throw new \InvalidArgumentException('The uid length must be an integer between 1 and 32');
        }

        $this->uid = substr(bin2hex(random_bytes((int) ceil($length / 2))), 0, $length);
    }

    public function __invoke(array $record): array
    {
        $record['extra']['uid'] = $this->uid;

        return $record;
    }

    /**
     * @return string
     */
    public function getUid(): string
    {
        return $this->uid;
    }
}

<?php declare(strict_types=1);

/*
 * This file is part of the Monolog package.
 *
 * (c) Jordi Boggiano <j.boggiano@seld.be>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Monolog\Processor;

/**
 * Adds a unique identifier into records
 *
 * @author Simon Mönch <sm@webfactory.de>
 */
class UidProcessor
{
    private $uid;

    public function __construct(int $length = 7)
    {
        if (!is_int($length) || $length > 32 || $length < 1) {
            throw new \InvalidArgumentException('The uid length must be an integer between 1 and 32');
        }

        $this->uid = substr(hash('md5', uniqid('', true)), 0, $length);
    }

    public function __invoke(array $record): array
    {
        $record['extra']['uid'] = $this->uid;

        return $record;
    }

    /**
     * @return string
     */
    public function getUid(): string
    {
        return $this->uid;
    }
}

--- 
+++ 
@@ -26,7 +26,7 @@
             throw new \InvalidArgumentException('The uid length must be an integer between 1 and 32');
         }
 
-        $this->uid = substr(hash('md5', uniqid('', true)), 0, $length);
+        $this->uid = substr(bin2hex(random_bytes((int) ceil($length / 2))), 0, $length);
     }
 
     public function __invoke(array $record): array
Make use of random_bytes for better uniqueness
