A function that calls the function with exact parameters' count.

CallFuncExact.php

<?php
/**
 * CallFuncExact.php
 *
 * @copyright 2018 koohq
 * @license https://creativecommons.org/publicdomain/zero/1.0/legalcode CC0
 */

/**
 * @param callable $func
 * @param mixed $args,...
 * @return mixed
 */
function callFuncExact(callable $func, ...$args)
{
    if (is_array($func)) {
        $rf = new ReflectionMethod(...$func);
    } elseif ($func instanceof Closure || function_exists($func)) {
        $rf = new ReflectionFunction($func);
    } else {
        $rf = new ReflectionMethod($func);
    }

    $params = $rf->getParameters();
    $numOfParams = count($params);

    if ($numOfParams === 0) {
        return call_user_func($func);
    }

    if ($params[$numOfParams - 1]->isVariadic()) {
        return call_user_func_array($func, $args);
    }

    $slicedArgs = array_slice($args, 0, $numOfParams);
    return call_user_func_array($func, $slicedArgs);
}

Sample.php

<?php

# A. PHP Warning
is_string(1, 2, 3);

# B. Without PHP Warning
callFuncExact('is_string', 1, 2, 3);
# is_string(1);