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Last updated: 2014-02-20
The following brief notes illustrate the architecture of PHPLint.
In the root of the PHPLint project there is a simple script
php for Unix/Linux) that starts the
currently installed PHP interpreter. This script, in turn, is used by
phpl under Unix/Linux) that finally starts
PHPLint, a PHP script located in
So, basically what you have to do to generate the PHPLint report about your
program is to type a command like this:
A simple GUI named
phplint.tcl is also available that displays the
report about a given source file and automatically updates this report as the
file timestamp changes, so that you may see the changes while editing and fixing
Under the stdlib/ directory there are several PHP source files: part are actually used by the PHPLint program itself, and part are provided for general usage in the hope them may be useful.
Generally, every source defines a single class and its namespace, and the namespace exactly matches the path of the file. So, for example, the file stdlib/it/icosaedro/bignumbers/BigInt.php contain the class it\icosaedro\bignumbers\BigInt. Every source loads the stdlib/autoload.php package that implements class autoloading: it is this package that maps class namespaces into file paths.
All the actual PHPLint program is under the
PHPLint.php the main program. The task of the main program
is to parse the command line parameters and to initialize all the classes of the
A description of the main classes follows.
Logger is responsible for the logging of the diagnostic
messages: errors, warnings and notices. Every message may refers to some specific
source location, so a concept of "where" something happened is required.
Where class stores the concept of where, in the source being
parsed, something happened. An object of this class contains: the file, the
line of the source, the number of that line and the exact position in the line.
Every object of this class stores a single position, and can be used to report
messages related to that position. The current position in the current source
being scanned is returned by the
here() method of the
Globals class holds the context of the parser, including the
list of the globally existing entities: packages, constants, variables,
functions and classes. A single instance of this class is created when the
program starts, and it is passed to every parser method.
Scanner is the PHPLint lexical scanner. In fact, PHPLint does not
uses the internal PHP scanner, but implements its own, independent, version
with some specific features not available from the built-in PHP scanner, like
support for meta-code keywords, character encoding checking, unclosed strings,
invalid escape sequences, user-friendly error reporting, abstract input source,
etc. And it is quite fast, as its scan rate is about 100 KB/s of PHP source on
a 2.6 GHz Pentium E5300 processor.
expressions\Expression is the parser of the expressions. All the
classes under the same namespace are related to this task. The most complicated
part is the correct handling of the variables, which is resolved splitting the
problem between parsing of unexisting variables (see
existing but not definitively assigned variables (see
UnassignedVar) and existing and assigned variables (see
AssignedVar). Each of these classes implements a
parse() method that perform its own task.
The distinction between existing but not assigned and existing and assigned variables
comes from the static flow analysis the program performs statement by statement
Flow for more about how PHPLint performs the static analysis).
types/Type is the abstract, base class that represents a type of
data. Some derived classes implement the well-known PHP types (boolean, int,
float, string, ...). The
UnknownType class is special, as it
represents something whose type cannot be determined by PHPLint. Generally,
when PHPlint cannot determine the exact type of an expression, an error is
logged in the report and a value of this type is set as the result of the
evaluation of the expression. Later, PHPLint avoids to report more errors
whenever that same unknown value is found again in the source.
Result class stores a type/value pair as may result from the
evaluation of an expression. Several methods also implements all the PHP
operators, so that some expressions, at least those involving only literal
values and constants, can be calculated.
statements/Statement and all the classes under this namespace
performs the parsing of the actual PHP source code. Some of these classes can be
easily recognized, like
ForStatement, and so on. Each of these classes provides a
method that parses the corresponding, specific, statement.
PHPLint 2, with more than 170 classes and hundreds of methods, is a quite large PHP project. While developing PHPLint 2, PHPLint 1 played its important role helping to master a so big, complex project. In fact, experience shown that once the source passes validation, it is also ready to work perfectly most of the times. This demonstrates how important validation is, and how much it contributes the quality of a program.
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