Call a user defined function given by the function parameter. Take the following:
<?php
function barber ($type) {
    print "You wanted a $type haircut, no problem";
}
call_user_func ('barber', "mushroom");
call_user_func ('barber', "shave");
?> | 
Object methods may also be invoked statically using this function by passing array($objectname, $methodname) to the function parameter.
<?php
class myclass {
  function say_hello() {
    print "Hello!\n";
  }
}
$classname = "myclass";
call_user_func(array($classname,'say_hello'));
?> | 
See also: is_callable(), call_user_func_array(), call_user_method(), call_user_method_array().