Articles/PHP

"Call to undefined function X()" in PHP — What It Means and How to Fix It

What the PHP error "Call to undefined function X()" means and how to fix it.

Published October 31, 2026

"Call to undefined function X()" occurs when code calls a function that doesn't exist or isn't loaded.

Key points

  • Common causes: a typo in the function name, or a required extension/library that isn't installed or included
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