PHP error guide

display_errors change does not show startup errors: meaning and fix

warning server Affects: PHP 7.4–8.4 Last verified:

Error summary

Enable protected logging in configuration; do not rely on ini_set inside a script to reveal parse or startup failures that occur before it runs.

What it means

Enable protected logging in configuration; do not rely on ini_set inside a script to reveal parse or startup failures that occur before it runs.

What the error means

display_errors controls response display but cannot retroactively show errors raised before the code calling ini_set was parsed or executed.

Why PHP produces it

The directive remains disabled in effective configuration, or the failure occurs during startup/parse before runtime overrides execute.

PHP version notes

The behavior described for display_errors change does not show startup errors applies to PHP 7.4–8.4 unless a narrower version is stated; exact wording can vary by SAPI and patch release.

Most common causes

  • ini_set is placed in the file that has a parse error.
  • A system-level setting cannot be changed at runtime.
  • display is off and log_errors has no writable destination.

Minimal examples

BAD — reproduces the problem

php 
ini_set("display_errors", "1")
this is invalid syntax

FIXED — safer pattern

ini 
display_errors=Off
log_errors=On
error_reporting=E_ALL

Step-by-step diagnosis

  1. Check directive access mode and effective value in the affected SAPI.
  2. Inspect web server, FPM, and PHP startup logs.
  3. Lint the file with the same PHP binary.

Fixes

Configure safe error logging before startup

Keep public display off in production and set a writable protected error log.

ini 
display_errors=Off
log_errors=On
error_reporting=E_ALL
error_log=/srv/app/var/php-error.log

Common mistakes when fixing it

  • Exposing production traces in HTML.
  • Assuming a blank page proves no error occurred.
  • Making the log world-readable.

How to prevent it

  • Configure logging before deployment.
  • Lint source in CI.
  • Monitor log write failures and disk space.

Web server / environment notes

fpm, apache, cli. Startup and parse diagnostics require configuration and server logs.

Tags: fpm,apache,cli

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