#syntax

PHP is partially case-sensitive. Variable names are case-sensitive, but function names, class names, and keywords (like if, else, while) ar…

Variables are declared using a dollar sign ($) followed by the variable name (e.g., $variable_name = value;).

PHP supports String, Integer, Float, Boolean, Array, Object, NULL, and Resource.

If a file is missing, include produces a warning and continues execution, while require produces a fatal error and stops execution.

Using the define() function or the const keyword.

It checks if a variable is set and is not NULL.