ForbidCountInLoopExpressions.md

ForbidCountInLoopExpressions

Detects usage of count() or sizeof() functions in loop condition expressions.

Using count() or sizeof() in loop conditions can cause performance issues or hard to trace bugs. This rule helps identify such cases.

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\ForbidCountInLoopExpressions\ForbidCountInLoopExpressionsRule

Examples

Default Configuration

<?php

class Example
{
    public function validLoopWithCachedCount(): void
    {
        $items = [1, 2, 3];
        $count = count($items); // ✓ Valid - count cached before loop
        
        for ($i = 0; $i < $count; $i++) {
            echo $items[$i];
        }
    }
    
    public function invalidForLoop(): void
    {
        $items = [1, 2, 3];
        
        for ($i = 0; $i < count($items); $i++) { // ✗ Error: Using count() or sizeof() in loop conditions can cause performance issues or hard to trace bugs.
            echo $items[$i];
        }
    }
    
    public function invalidWhileLoop(): void
    {
        $items = [1, 2, 3];
        $i = 0;
        
        while ($i < count($items)) { // ✗ Error: Using count() or sizeof() in loop conditions can cause performance issues or hard to trace bugs.
            echo $items[$i++];
        }
    }
    
    public function invalidDoWhileLoop(): void
    {
        $items = [1, 2, 3];
        $i = 0;
        
        do {
            echo $items[$i++];
        } while ($i < sizeof($items)); // ✗ Error: Using count() or sizeof() in loop conditions can cause performance issues or hard to trace bugs.
    }
    
    public function complexCondition(): void
    {
        $items = [1, 2, 3];
        
        for ($i = 0; $i < count($items) - 1; $i++) { // ✗ Error: Using count() or sizeof() in loop conditions can cause performance issues or hard to trace bugs.
            echo $items[$i];
        }
    }
    
    public function validCountInLoopBody(): void
    {
        $items = [1, 2, 3];
        
        for ($i = 0; $i < 3; $i++) { // ✓ Valid - condition doesn't use count()
            $total = count($items); // ✓ Valid - count in loop body is not checked
            echo $total;
        }
    }
}

Important Notes

• This rule only checks loop conditions, not loop bodies
• Both count() and sizeof() functions are detected
• Applies to for, while, and do-while loops
• Only reports the first occurrence per loop to avoid duplicate errors
• Nested loops are checked independently
• Only checks global count() and sizeof() functions, not method calls like $obj->count()