Challenge 1 — Solution

Task: Write a function squareRoot($n) that throws an Exception if $n is
negative (square roots of negative numbers aren't real numbers),
otherwise returns sqrt($n). Call it inside a try/catch with both a
valid and an invalid value, echoing either the result or the caught
error message.

<?php
    function squareRoot(float $n): float {
        if ($n < 0) {
            throw new Exception("Cannot take the square root of a negative number: $n");
        }
        return sqrt($n);
    }

    try {
        echo squareRoot(16) . "<br>";
        echo squareRoot(-4) . "<br>";   // this line throws
    } catch (Exception $e) {
        echo "Error: " . $e->getMessage();
    }
?>


Output:
4
Error: Cannot take the square root of a negative number: -4

Notes:
- squareRoot(16) succeeds and echoes normally, since 16 is non-negative
  - execution continues into the try block's second line.
- squareRoot(-4) throws before it ever returns a value, immediately
  jumping to the catch block - the "echo squareRoot(-4)" line's own
  echo never actually completes, since the exception interrupts it.
- Only one message from the try block ever reaches the catch block,
  even though there could in principle have been multiple calls that
  might throw - the very first exception thrown stops the rest of the
  try block from running at all.