Identifying repeated code within PHP project

Question

I have a single PHP file within a legacy project that is at least a few thousand lines long. It is predominantly separated up into a number of different conditional blocks by a switch statement with about 10 cases. Within each case there is what appears to be a very similar - if not exact duplicate - block of code. What methods are available for me identifying these blocks of code as being either the same - or close to the same - so I can abstract that code out and begin to refactor the entire file? I know this is possible in very manual terms (separate the code into files and Diff) but i'm interested in what tools i could be using to speed this up.

Thanks.

Answer 1

You can use phpunit PMD (Project Mess Detector) to detect duplicated blocks of code.

It also can compute the Cyclomatic complexity of your code.

Here is a screenshot of the pmd tab in phpuc:

Answer 2

You could put the blocks in separate files and just run diff on them?

However, I think in the end you will need to go through everything manually anyway, since it sounds like this code requires a lot of refactoring, and even if there are differences you will probably need to evaluate whether this is intentional or a bug.

Answer 3

You can use phpcpd.

phpcpd is a Copy/Paste Detector (CPD) for PHP code. It scans a PHP project for duplicated code.

Further resources:

• http://qualityassuranceinphpprojects.com/pages/tools.html

Answer 4

See our PHP Clone Detector tool.

This finds both exact copies and near misses, in spite of reformatting, insertion/deletion of comments, replacement of variable names, addition/replacments of subblocks etc.

PHPCPD as far as I can tell finds only sequences which are exactly the same. That misses a lot of clones, since the most common operation after copy-paste is edit-to-customize. So it would miss the very clones the OP is trying to find.