Unreachable Code

Unreachable code refers to a section of code within a program that can never be executed during the program’s runtime. It means that the code is written in such a way that it can never be reached or accessed by the program’s execution flow.

Unreachable code can occur due to several reasons:

• Conditional statements

• Early return statements

• Infinite loops

• Branching with goto, yield, break, return, die…

<?php

    $a = 1;
    echo foo($a);

    exit;

    // This is unreachable code, as it will never be executed
    echo $a;

    // This is not unreachable, as PHP scoops the definition at linting time
    function foo($s) {
        return strtolower($s);
    }

?>

Documentation

Related : Dead Code