PHP: Code checker since PHP is a loose type / dynamic language?

Question

I have a small PHP web-based application that is beginning to grow moderately in size.

I'm starting to become concerned with managing my PHP code base, given PHP is a loosely/weak typed, dynamic language.

How do others manage their code based for loosely/weak typed, dynamic languages?

Do pre-parsers exist for PHP that allow me to runs checks on my code base to identity such things like below?

$var1 = 'data';
// vr1 doesn't exist, it's a typo of $var1, but PHP would allow for this and not complain
echo $vr1;

UPDATE:

The example above might not be the best example but essentially, what I'm trying to convey is that certain errors in a dynamically weak typed language would only be found when the code is run in production at RUN TIME; whereas, some of these issues would typically be found in strongly typed static languages at COMPILE time.

How can I also find these non-algorithm type of errors in PHP prior to moving my code into production without having to create an insane number of Unit Tests?

As such, does anything exist where I can run my PHP code through it, prior to moving into production, and this pre-processor parses my code to ensure I'm only using defined variables, etc. Essentially, check my code for validation for non-algorithmic type of uses. E.g. not trying perform algebra on a string, etc.

UPDATE 2

Please note, this question is still not answered because I'm looking for a way to identity these type of non-algorithmic errors in PHP at "compile" type, not RUN TIME.

Answer 1

You can lint your PHP with php -l filename.php. This would show any syntax errors. There is IDEs out there that will lint while you write the code. Those usually can also detect issues like shown in your question in addition to linting.

Apart from this, consider writing UnitTests for your code to ensure functionality and have a look at http://phpqatools.org for a number of other tools that can assist you in increasing code quality.

Make sure you have error_reporting(-1); set during development to enable all errors, in addition to enable display_errors and display_startup_errors in php.ini. Disable the latter two on your production system to prevent exposure of server information.

Edit after update: PHP source code is compiled on-the-fly. PHP's compile time is effectively at run time. If you want compiled PHP, you have to use Facebook's HipHop.

Answer 2

PHP will definitely complain about that with either a warning or a notice if you set your error_reporting config directive appropriately.

See:

https://www.php.net/manual/en/errorfunc.configuration.php#ini.error-reporting

Answer 3

That type of error would be caught if you set error reporting to the max. It would give a Notice indicating that $vr1 wasn't set.

You can set error reporting in your php.ini file, or on individual pages using the ini_set() function.

Answer 4

The closest thing is php's lint checker, but that's more of a syntax checker. You can run lint from a command line:

php -l path/to/file.php

You could build this into your file repository system by setting up a pre-commit check.

Answer 5

Runtime Errors

Uninitialized variables are runtime errors (of level E_NOTICE) in PHP, so you can only see them at runtime. The example you gave may or may not end up erroring, depending on how the code is executed. For instance, it could be that $vr1 is defined in a conditional include() that is sometimes included and sometimes not.

Additionally, it's possible to dynamically create variables at runtime using variable variables ($$var), so again that $vr1 may actually be defined somewhere. If the PHP interpreter failed to run valid syntax, or gave compiler errors on valid syntax, that would be a different sort of problem.

You might compare the uninitialized variable circumstance to a divide by zero error. It's not an error unless it actually happens.

Compiletime errors are E_PARSE, E_COMPILE_ERROR, or E_COMPILE_WARNING (not fatal) in PHP. These include things like missing files, functions, or classes, i.e. trying to execute code that isn't there—something PHP can't possibly do. If PHP may be able to, it will try.

Detection and Prevention

At the very least, you should make sure that your development and testing environments have all of the PHP error junk turned on in the ini:

error_reporting = E_ALL|E_STRICT
display_errors = On

Or at runtime:

error_reporting(-1);

Self Discipline

A few tips for working with PHP that might help:

• Use functional programming
• Establish code smells and write clean syntax
• Do your own type checking (OOP and functional programming can make this easier)
• Avoid the global scope and include()-based control structures
• Use an IDE with code awareness aids, like Netbeans.

For instance, in your example above, if you have to pass your variable into a function or method that checks that the parameter isset() or !== nullbefore using it, you can avoid or mitigate the problem of uninitialized variables.

Resources

• Comparison operators (see Identity, specifically)
• Type comparison tables
• is_int(), is_float(), etc.

Answer 6

As PHP is not usually considered to go through a separate COMPILE process perhaps you could explain at what point you consider your code to be COMPILED?

Answer 7

Here's another SO question that focuses on PHP code analysis tools.

Answer 8

1. Hack is a statically typed language created by Facebook which is essentially PHP with many features added and removed.
2. PhpStorm is an IDE which provides "inspections" which catch many things that would be caught by a static type checker, such as the undefined variable in your example.
3. I started writing a static type checker for PHP here based on PHP7 type hints and PHPDoc annotations. I never finished it but there are some passing tests and the design so far seems to be sound.