I have two somewhat general questions about the PHP 5
language. These points remain unclear to me after reading
the manual and working with the language for a few months:
i) Does the language provide a way to generate a private or
local class that is accessible only within another function
or a parent class. In python, for example, if you declare a
class or function within a function definition, I believe it
is accessible only within the parent function. Does PHP 5
supply a good way to generate a little utility class without
polluting the public namespace? Or are local variables in
functions, class methods and class properties the only
entities that can be hidden from public access?
ii) Suppose I would like to be able generate any of several
classes at runtime, for which constructor interfaces are the
same. These might, for example, be specialized subclasses of
a common parent. Based on the idea of a variable variable,
I am tempted to try to replace the class name by a variable,
as in
$object = new $class_name_variable($param1,$param2,....)
Is this legal PHP 5? Put another way, are variable names the
only identifiers that can be replaced by string values of
other variables, or is the technique more general? For instance,
how about accessing a property or method by a name that is
specified by a variable, as in:
$object_instance->$property_name_variable
or
$object_instance->$method_name_variable()
The idea of a 'variable variable' name seems quite useful,
but I'm not sure how general the concept is. Is there a
well-defined rule for when the parser will accept a string
value of a variable as a replacement for a literal
identifier. If so, is the rule documented?
Thanks in advance for any insight.
-David Morse
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! David Morse email: morse@xxxxxxxxxxxx !
! Dept of Chem Eng & Mat Sci phone: (612)625-0167 !
! University of Minnesota !
! Minneapolis, MN 55455 !
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