PHP error guide

Xdebug invalid mode: meaning and fix

warning server Affects: Xdebug 3.x except the nesting-level legacy page Last verified:

Error summary

Use supported comma-separated modes such as develop,debug or profile. Xdebug.mode contains a value not recognized by Xdebug 3.

What it means

Use supported comma-separated modes such as develop,debug or profile. Xdebug.mode contains a value not recognized by Xdebug 3.

What the error means

This message means that xdebug.mode contains a value not recognized by Xdebug 3. The exact signature distinguishes xdebug invalid mode from a generic application failure.

Why PHP produces it

The engine or service reports “Xdebug invalid mode” because its required precondition was not met. Use supported comma-separated modes such as develop,debug or profile.

PHP version notes

The xdebug invalid mode wording here is based on Xdebug 3.x except the nesting-level legacy page; 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: xdebug.mode contains a value not recognized by Xdebug 3
  • The code path assumes the prerequisite for xdebug invalid mode has already been satisfied.
  • For xdebug invalid mode, 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 xdebug invalid mode.

Minimal examples

BAD — reproduces the problem

ini 
xdebug.mode=debugger

FIXED — safer pattern

ini 
xdebug.mode=develop,debug

Step-by-step diagnosis

  1. Copy the complete “Xdebug: [Config] Invalid mode 'debugger' set for 'xdebug.mode' configuration setting” text and retain the first application stack frame.
  2. Reproduce xdebug invalid mode in the same SAPI and environment listed for this page.
  3. Before changing xdebug invalid mode, inspect the preceding value or directive and verify its type, path, version, and permissions.
  4. Apply the narrow correction—use supported comma-separated modes such as develop,debug or profile—then repeat the original request once.

Fixes

Correct the failing prerequisite

Use supported comma-separated modes such as develop,debug or profile

ini 
xdebug.mode=develop,debug

Fail explicitly at the boundary

Validate the condition before the operation that emits xdebug invalid mode, and log a safe diagnostic without credentials or full production paths.

Common mistakes when fixing it

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

How to prevent it

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

Web server / environment notes

fpm, cli, docker, linux. The failure occurs where xdebug.mode contains a value not recognized by Xdebug 3

Tags: fpm,cli,docker,linux

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