Rule source on GitHub

DowngradeClampRector

Replace clamp() with min()/max().

-clamp($value, $min, $max);
+max($min, min($max, $value));

Configure your rector.php:

<?php

use Rector\Config\RectorConfig;
use Rector\DowngradePhp86\Rector\FuncCall\DowngradeClampRector;

return RectorConfig::configure()
    ->withRules([
        DowngradeClampRector::class,
    ]);