if-else and switch in PHP

Why we need decisions

A program often has to choose what to do based on a value. Should it show "Pass" or "Fail"? Is the user an adult or a minor? These choices are made with conditional statements — if, elseif, else and switch. They let the code take different paths for different situations.

The if statement

if runs a block of code only when its condition is true.

<?php
  $age = 20;
  if ($age >= 18) {
      echo "You are an adult";
  }
?>

If the condition is false, PHP simply skips the block and moves on.

if - elseif - else

Add else for the "otherwise" case, and elseif for extra conditions in between.

<?php
  $marks = 75;
  if ($marks >= 90) {
      echo "Grade A";
  } elseif ($marks >= 60) {
      echo "Grade B";
  } else {
      echo "Grade C";
  }
?>

PHP checks the conditions top to bottom and runs the first one that is true, then skips the rest. Since 75 is not ≥ 90 but is ≥ 60, "Grade B" runs.

The switch statement

When you compare one variable against several exact values, switch is cleaner than many elseifs.

<?php
  $day = 3;
  switch ($day) {
      case 1: echo "Monday";    break;
      case 2: echo "Tuesday";   break;
      case 3: echo "Wednesday"; break;
      default: echo "Other day";
  }
?>

Each case ends with break so only the matching one runs. default handles anything that did not match.

Short if (ternary)

For a simple either/or, the ternary operator does it in one line.

<?php
  $age = 16;
  $msg = ($age >= 18) ? "Adult" : "Minor";
  echo $msg;
?>

Read it as: condition ? value-if-true : value-if-false. Great for short decisions, but for anything complex a full if-else is more readable.

Common mistakes

• Using = instead of ==. if ($x = 5) assigns and is always true; use ==.
• Forgetting break in switch. Without it, later cases also run (fall-through).
• Wrong condition order. Put stricter conditions first, or a looser one may catch the value early.
• Missing curly braces. Always use { } so it is clear which lines belong to the if.

Summary

• if runs code when a condition is true; else handles the rest.
• elseif adds more conditions; PHP runs the first true one.
• switch compares one variable to exact values — use break in each case.
• The ternary ? : is a one-line if-else for simple choices.
• Always use ==/=== in conditions, not =.

Next, repeat actions with loops in PHP, or review PHP operators used inside conditions.