<?php
class Class1 { static function addMethod() { echo "Class1::add() called!\n"; } }
class Class2 { static function readMethod() { echo "Class2::read() called\n"; } }
 
$arr=array(
    "add" => [Class1::class, "addMethod"],
    "read"=> [Class2::class, "readMethod"],
);
 
$keys = ["add", "non-existing", "read"];
 
foreach($keys as $key) {
	if(array_key_exists($key, $arr)) {
		call_user_func($arr[$key]);
	} else {
		echo "default, nothing called\n";
	}
}

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