Assign Null In Function Call

ID

php.assign_null_in_function_call

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Php

Tags

reliability, suspicious-call

Description

Reports assignments that capture the result of a free function which never returns a value — either because it declares a void return type or because its body has no value-bearing return. Such a call evaluates to null, so the assigned variable holds nothing useful.

Rationale

A function that performs only side effects (logging, printing, mutating state) returns null in PHP. Assigning that null to a variable reads as if the call produced a result, which misleads the reader and hides the fact that the variable is always empty. The pattern usually means the caller misunderstood the function’s contract or expected a different function. Calls to functions that do return a value, or that declare a non-void return type, are left alone.

<?php
function logMessage($msg)
{
    echo $msg;            // no return — yields null
}

function compute($a, $b)
{
    return $a + $b;
}

$a = logMessage('hello'); // FLAW — logMessage returns no value, $a is null
$b = compute(1, 2);       // OK — compute returns a value
logMessage('plain');      // OK — result is not captured

Remediation

Call the function as a statement instead of assigning its result. If you genuinely need a return value, make the function return one (and declare its return type) or call a function that provides the value you expect.

References