Conditions: if, else & switch

if / elseif / else

An if statement runs a block of code only when a condition is true. elseif offers another condition to try if the first was false, and else is the fallback that runs when nothing above matched. PHP checks the conditions from top to bottom and stops at the first one that is true.

<?php
  $marks = 72;
  if ($marks >= 75) {
    echo "Grade A";
  } elseif ($marks >= 50) {
    echo "Grade B";
  } else {
    echo "Fail";
  }
?>

Step by step with $marks set to 72: PHP first asks "is 72 ≥ 75?" — no, so it skips Grade A. Next it asks "is 72 ≥ 50?" — yes, so it prints Grade B and stops without ever reaching else. The braces { } mark where each block begins and ends.

switch

When you are comparing one variable against many fixed values, a switch is tidier than a long chain of elseif. It checks each case in turn; break stops it once a match is found, and default runs if nothing matched.

<?php
  $day = "Mon";
  switch ($day) {
    case "Mon": echo "Monday"; break;
    case "Tue": echo "Tuesday"; break;
    default: echo "Another day";
  }
?>

Here $day is "Mon", so PHP jumps to case "Mon", prints Monday, and the break exits the switch. If $day had been "Sun", no case would match and default would print Another day.