If your imagejpg, imagepng, or imagegif functions can generate images but fail to display them in the browser, this article will help you resolve the issue.
Initially, I compared a working file with the problematic one and found no visible differences - not even a single character.
Undeterred, I downloaded a text comparison tool. The truth gradually emerged:
As shown, the left (working) file uses standard UTF-8, while the right (problematic) file uses UTF-8 + BOM.
Key differences between the encodings:
UTF-8+BOMincludes a three-byte prefix (0xEF 0xBB 0xBF) absent in standardUTF-8. While this prefix helps programs automatically detect UTF-8 encoding, it causes critical issues in PHP:
The extra three bytes trigger output before PHP’sheader()function, violating its requirement of “no output before headers”. This prevents proper image rendering in browsers.
Solution: Convert file encoding to standard UTF-8 (without BOM) using your code editor or IDE.