IfStatementAssignment.md

IfStatementAssignment

Detects assignments inside if and elseif conditions.

Assignments in if conditions are a code smell. They can easily mask logic errors, particularly typos where = was written instead of == or ===. Additionally, when the assigned value is falsy (e.g., 0, null, false, or an empty string), the condition will silently always evaluate to false, leading to bugs that can be difficult to spot. All assignment forms are flagged: plain assignment (=), reference assignment (=&), and compound assignments (+=, ??=, .=, etc.).

Configuration

This rule has no configuration options.

Usage

Add the rule to your PHPStan configuration:

includes:
    - vendor/orrison/meliorstan/config/extension.neon

rules:
    - Orrison\MeliorStan\Rules\IfStatementAssignment\IfStatementAssignmentRule

Examples

Default Configuration

<?php

// ✗ Error: Avoid assignments inside if and elseif conditions.
if ($foo = someFunction()) {
    // ...
}

// ✗ Error: Avoid assignments inside if and elseif conditions.
if ($bar = 0) {
    // ...
}

// ✗ Error: Avoid assignments inside if and elseif conditions.
if ($ref = &$source) {
    // ...
}

// ✗ Error: Avoid assignments inside if and elseif conditions.
if ($count += 1) {
    // ...
}

// ✗ Error: Avoid assignments inside if and elseif conditions.
if (($baz = someFunction()) && $other) {
    // ...
}

// ✗ Error: Avoid assignments inside if and elseif conditions.
if ($x > 1) {
    // ...
} elseif ($result = otherFunction()) {
    // ...
}

// ✓ Valid: assign before the condition
$foo = someFunction();
if ($foo) {
    // ...
}

// ✓ Valid: comparisons are allowed
if ($value === null) {
    // ...
}

// ✓ Valid: compound conditions without assignments
if ($a && $b) {
    // ...
}

Important Notes

• All assignment forms are detected: plain =, reference =&, and compound operators (+=, ??=, .=, etc.).
• Assignments are detected recursively throughout the condition expression, including those nested inside compound conditions with &&, ||, and parentheses.
• Both if and elseif conditions are checked.
• while loop conditions are not checked by this rule.
• To use the result of a function call as both an assigned value and a condition, assign it on a separate line before the if statement.