3.0 KiB
About Psalm
Psalm is a static analysis tool that attempts to dig into your program and find as many type-related bugs as possible.
It has a few features that go further than other similar tools:
-
Mixed type warnings
If Psalm cannot infer a type for an expression then it uses amixedplaceholder type.mixedtypes can sometimes mask bugs, so keeping track of them helps you avoid a number of common pitfalls. -
Intelligent logic checks
Psalm keeps track of logical assertions made about your code, soif ($a && $a) {}andif ($a && !$a) {}are both treated as issues. Psalm also keeps track of logical assertions made in prior code paths, preventing issues likeif ($a) {} elseif ($a) {}. -
Property initialisation checks
Psalm checks that all properties of a given object have values after the constructor is called.
Psalm also has a few features to make it perform as well as possible on large codebases:
-
Multi-threaded mode
Whereever possible Psalm will run its analysis in parallel to save time. Useful for large codebases, it has a massive impact on performance. -
Incremental checks
When using the--diffcommand line option, Psalm will only analyse files that have changed and files that reference them.
Example output
Given a file implode_strings.php:
<?php
$a = ['foo', 'bar'];
echo implode($a, ' ');
> ./vendor/bin/psalm implode_strings.php
ERROR: InvalidArgument - somefile.php:3:14 - Argument 1 of implode expects `string`, `array` provided (see https://psalm.dev/004)
Inspirations
There are two main inspirations for Psalm:
- Etsy's Phan, which uses nikic's php-ast extension to create an abstract syntax tree
- Facebook's Hack, a PHP-like language that supports many advanced typing features natively, so docblocks aren't necessary.
Index
- Running Psalm:
- Annotating code:
- Manipulating code: