php 5.3 – How to use call_user_func in PHP-ThrowExceptions

Hi call_user_func is used in my existing code but it is throwing an INTERNAL SERVER ERROR

$out=call_user_func($func);

$func variable has an array like this.

Array
    (
        [0] => MetricName Object
            (
                [idplot] => 
                [_idtestType:MetricName:private] => 
                [data] => 
                [idmetricName] => 
                [queriesForIds:MetricName:private] => Array
                    (
                        [idviewType] => SELECT column FROM Table WHERE idColumn = 
                        [idworstCase] => SELECT column2 FROM Table2 WHERE idColumn = 
                    )

            )

        [1] => update
    )


class MetricName { 
    function update() { 
      //Its not possible to add the code inside the update method
    }
}

This method is throwing INTERNAL SERVER ERROR

Undefined index: environment

Don’t know how to fix this error.

<?php
class MetricName { 
    function update($ds) { 
     print_r($ds);
    }
}

$func =  [
  new MetricName(),'update',
];

call_user_func_array ($func,['234']);
?>