Lesson 6 — Control Flow

Conditional Statements

Conditional statements let a PHP script branch its behaviour based on whether an expression evaluates to true or false.

if, elseif, else

PHP's conditional syntax closely mirrors C-style languages, with elseif written as one word (unlike some languages that use two).

PHP — Conditional logic 
$mark = 74;

if ($mark >= 80) {
    echo "Distinction";
} elseif ($mark >= 60) {
    echo "Merit";
} elseif ($mark >= 50) {
    echo "Pass";
} else {
    echo "Fail";
}

The Ternary and Switch

The ternary operator offers a compact one-line conditional for simple cases. switch is useful when comparing one variable against several possible exact values.

PHP — Ternary operator 
$status = $isActive ? "Active" : "Inactive";

Common Mistakes

  • Writing 'else if' as two words when PHP expects 'elseif' as one word in the standard alternative — both actually work in PHP, but mixing conventions inconsistently hurts readability.
  • Forgetting break in a switch case, causing fall-through into the next case.
  • Overusing the ternary operator for complex conditions, making code harder to read rather than easier.
  • Using assignment (=) instead of comparison (==/===) inside an if condition by mistake.

Professional Tip

Reserve the ternary operator for genuinely simple assignments, like setting a default or toggling between two short strings. For anything with nested logic, a full if/else block stays far more readable.

Your Turn

Write a script that determines a shipping cost based on an order total using if/elseif/else, then rewrite the simplest branch using a ternary operator instead.

Mini Quiz

What must you include at the end of each switch case to prevent fall-through in PHP?