Which constant in PHP returns the current line number where it is called?

The constant that returns the current line number where it is called is LINE. This is a built-in magic constant in PHP, which means it is predefined in the language and automatically provides information about the code's context at runtime.

When LINE is used in a script, it evaluates to the line number of that particular line of code. This can be particularly useful for debugging and logging purposes, as developers can quickly find where issues may be occurring in their scripts. Unlike the other options, which are not defined in PHP, LINE serves a specific function that enhances code readability and maintainability by directly linking the line number to the code being executed.

To clarify, the other options do not exist in PHP: current_line() and get_line() do not return line numbers, and line_number() is also not recognized as a valid constant or function in the PHP language.