Perl vs. PHP

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computing: software: Perl: Perl vs. PHP
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Perl and PHP are often compared with each other, largely due to their mutual popularity for web site design. The general consensus seems to be that people use PHP because it was invented specifically for creating web pages, whereas Perl has a lot of other uses as well — or, in other words, people use PHP because they don't know any better, and people who know better use Perl.

Unfortunately, this apparently does nothing to prevent the use of PHP in such heavily-used, highly-developed applications as MediaWiki and Drupal.


Object-Oriented Programming

object-oriented programming, or OOP, was a late addition to both languages, but it's a bit easier to use in PHP. (Perl's implementation is being dramatically improved for Perl 6, in development as of January 2007.) A comparison:

characteristic Perl PHP
class files typically one class per file,
but multiple classes are possible
multiple classes per file
class initialization code
my $self  = {};
$self->{'FIELDNAME'} = default;
return $self;
$this->fieldname = default;
initialization code within methods my $self = shift; none needed
identifier within class code $self->fieldname
  • this->$fieldname for per-object data
  • self::$fieldname for static data
  • this->method() for calling method dynamically
  • self::method() for calling method statically

OOP Notes

  • In class methods, the object itself is an implicit first argument; the shift function uses the @_ magic variable by default, effectively retrieving the object reference.
  • The Perl bless function causes the package's functions to be bound into the hashref object (probably creates a VMT for it); without being blessed, the object is just a normal hashref.
  • On the surface, PHP's identifier-within-class syntax seems more complicated, but it made intuitive sense to me (Woozle) except possibly for the issue of which identifiers get dollar-signs and which don't (which is even more complicated in Perl)... although I don't see why PHP needs both "this" and "self" when there's the "->" vs. "::" to disambiguate dynamic from static (but again, this is a minor annoyance and much less confusing than many aspects of Perl's OOP syntax).
  • In Perl, any string inside delimiters (such as [], {}, ()) is assumed to be a string literal if it does not begin with $ and does not contain any delimiters. (This is a rough guess at the actual rules, which may be more complicated.) For this reason, some examples of class initialization show the field names without quotes, e.g. "$self->{FIELDNAME} = 'value';", which can be more understandably written as "$self->{'FIELDNAME'} = default;".
  • Apparently the OOP syntax in Perl 6 (currently in development) is much improved and more intuitive; the OOP syntax in Perl 5 is more like grafting OOP onto a basically procedural language.


Porting from PHP to Perl

  • PHP::Interpreter: a Perl module for running PHP code
  • PHP::Strings: a Perl module that implements most of the PHP String functions (those which are not implemented are generally trivial, and are stubbed with a message explaining this)