Boolean Compare With Literal

ID

php.boolean_compare_with_literal

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Code Smell

Language

Php

Tags

code_smell, suspicious-comparison

Description

Reports a strict comparison (=== or !==) in which one operand is the boolean literal true or false, such as $flag === true or $done !== false. These comparisons add no information and read worse than testing the boolean directly.

Rationale

When the operand is already a boolean, comparing it to a literal is redundant: $flag === true is equivalent to $flag, and $flag !== false is also equivalent to $flag. Dropping the literal makes the condition shorter and clearer, and removes a common copy-paste source of inverted logic (=== false vs !== false).

This rule covers only the strict operators. Loose comparisons against a boolean literal ($x == true, $x != false) are reported by the strict-comparison rule, so scoping this rule to ===/!== keeps the two from flagging the same line twice.

<?php
if ($flag === true) {   // FLAW - redundant, write if ($flag)
    run();
}

if ($flag !== false) {  // FLAW - redundant, write if ($flag)
    run();
}

if ($flag) {            // OK - direct boolean test
    run();
}

Remediation

Test the boolean directly. Replace $x === true and $x !== false with $x, and replace $x === false and $x !== true with !$x.

References