Inefficient membership test (ARCH7075)

Key php.performance.inefficient-membership-test · Severity warning · Category performance

Checking membership with in_array() over a list, especially inside a loop, scans O(n) each time. Use a keyed map and isset() for an O(1) lookup.

Incorrect

<?php
$allowed = ['admin', 'editor', 'viewer'];
foreach ($users as $user) {
    if (in_array($user->role, $allowed, true)) {
        $granted[] = $user;
    }
}

Correct

<?php
$allowed = ['admin' => true, 'editor' => true, 'viewer' => true];
foreach ($users as $user) {
    if (isset($allowed[$user->role])) {
        $granted[] = $user;
    }
}

Fix

For repeated membership checks, convert the list to a keyed map and query it with isset().