// notes/

Debugging

Coding tips and build notes by Mahir Faysal, a student web developer in Bangladesh: tested Python, HTML, CSS, JavaScript and PHP tutorials, plus notes from my Next.js and Gemini projects. Sample posts are marked and drafts stay in the admin area.

All notes Coding tips · 67 Learning notes · 4 Practice · 1

Coding tips

PHP “Cannot modify header information – headers already sent”: 6 Causes and Fixes (Tested)

PHP’s ‘Cannot modify header information – headers already sent’ warning means something was output before header() or session_start(). How to read ‘output started at’, and fixes for spaces, BOMs, echo, closing tags, includes and output buffering. Tested.

October 12, 2026 · 11 min read · 0 views

// filter

You are inside a slice of the notes.

This view is only the category, tag, or search you asked for. Sample warnings still apply on any article that carries them. Drafts are still hidden. The full list is the learning notes page, which also explains how a note is written and why some posts are marked Sample.