Missing Param Type

ID

php.missing_param_type

Severity

info

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

Php

Tags

code_smell, type-safety

Description

Reports parameters of a named function or method that have no type declaration. Since PHP 7.0 every parameter can declare a scalar, class, nullable (?int) or union (int|string) type, and an undeclared parameter leaves the function’s contract weaker than it needs to be.

Rationale

A parameter without a declared type forces every reader and every caller to infer what the function expects, and it disables the engine’s own argument-type checks: a mismatched value is only discovered when it triggers a fault deep inside the body. Declaring the type documents the contract, lets the runtime reject bad calls at the boundary, and unlocks accurate static analysis.

Variadic (…​$rest) and by-reference (&$value) parameters are flagged too, because they carry values that benefit from a declared type just like ordinary parameters. Closures and arrow functions are not inspected, and the magic methods whose signatures PHP fixes (get, set, call, callStatic, isset, unset) are exempt.

<?php
function discount($price, float $rate)  // FLAW — $price has no type declaration
{
    return $price * (1 - $rate);
}

function total(float $price, float $rate): float  // OK — every parameter is typed
{
    return $price * (1 + $rate);
}

Remediation

Add the most specific type the parameter accepts. Use a scalar (int, float, string, bool), a class or interface name, a nullable type (?Type) when null is allowed, or a union (int|string) when several types are valid.

References