PHP error guide

Return value must be of type: meaning and fix

fatal type Affects: PHP 8.x Last verified:

Error summary

Return the declared type on every path or declare a nullable type when null is meaningful. A function returns a value incompatible with its declared return type.

What it means

Return the declared type on every path or declare a nullable type when null is meaningful. A function returns a value incompatible with its declared return type.

What the error means

This message means that a function returns a value incompatible with its declared return type. The exact signature distinguishes return value must be of type from a generic application failure.

Why PHP produces it

The engine or service reports “Return value must be of type” because its required precondition was not met. Return the declared type on every path or declare a nullable type when null is meaningful.

PHP version notes

The return value must be of type wording here is based on PHP 8.x; punctuation and exception class names can differ on older branches or vendor builds.

Most common causes

  • The immediate input or configuration reaches the specific condition: a function returns a value incompatible with its declared return type
  • The code path assumes the prerequisite for return value must be of type has already been satisfied.
  • For return value must be of type, development and production differ in version, extension, permissions, paths, or service configuration.
  • An earlier operation returned an unchecked value that is consumed by the line reporting return value must be of type.

Minimal examples

BAD — reproduces the problem

php 
function findName(): string { return null; }

FIXED — safer pattern

php 
function findName(): ?string { return null; }

Step-by-step diagnosis

  1. Copy the complete “Fatal error: Uncaught TypeError: findName(): Return value must be of type string, null returned” text and retain the first application stack frame.
  2. Reproduce return value must be of type in the same SAPI and environment listed for this page.
  3. Before changing return value must be of type, inspect the preceding value or directive and verify its type, path, version, and permissions.
  4. Apply the narrow correction—return the declared type on every path or declare a nullable type when null is meaningful—then repeat the original request once.

Fixes

Correct the failing prerequisite

Return the declared type on every path or declare a nullable type when null is meaningful

php 
function findName(): ?string { return null; }

Fail explicitly at the boundary

Validate the condition before the operation that emits return value must be of type, and log a safe diagnostic without credentials or full production paths.

Common mistakes when fixing it

  • Suppressing return value must be of type instead of correcting its upstream condition.
  • Testing return value must be of type only with the CLI binary when the failing request runs under FPM or Apache.
  • Changing a global setting for return value must be of type before confirming the site-specific effective configuration.

How to prevent it

  • Add a focused test that exercises the boundary responsible for return value must be of type.
  • Keep runtime versions, extensions, configuration, and deploy artifacts affecting return value must be of type reproducible.
  • Validate external data and service return values before they can trigger return value must be of type.

Web server / environment notes

cli, fpm, linux. The failure occurs where a function returns a value incompatible with its declared return type

Tags: cli,fpm,linux

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