%s(): Passing null to parameter #%d (%s) of type string is deprecated

Description

Since PHP 8.1, PHP has been enforcing non-null parameters to PHP native functions. Until then, it was possible to use NULL everywhere, and it would have been cast to an empty string or 0. Nowadays, it is a deprecation.

This applies to all PHP native functions, such as, and not limited to: strtolower(), strip_tags(), trim(), addslashes(), strlen(), rtrim(), etc.

Example

<?php

strlen(null);

?>

Literal Examples

• strlen(): Passing null to parameter #1 ($string) of type string is deprecated

Solutions

• Check the value before calling the function.

• Use ?? to convert the null into a suitable default value.