PHP — If Else

Basic if statement

Execute code only when a condition is true:

<?php
$temperature = 28;

if ($temperature > 25) {
    echo "It's warm outside!";
}
?>

The condition is evaluated as a boolean. PHP treats these values as falsy:

<?php
// All falsy values:
false
0
0.0
""
"0"
null
array()
// empty object (PHP 8+)
?>

Everything else is truthy, including non-empty strings, non-zero numbers, and arrays with elements.

if-else

Provide an alternative path:

<?php
$hour = 14;

if ($hour < 12) {
    echo "Good morning!";
} else {
    echo "Good afternoon!";
}
// Output: Good afternoon!
?>

if-elseif-else

Check multiple conditions in sequence:

<?php
$score = 85;

if ($score >= 90) {
    $grade = "A";
} elseif ($score >= 80) {
    $grade = "B";
} elseif ($score >= 70) {
    $grade = "C";
} elseif ($score >= 60) {
    $grade = "D";
} else {
    $grade = "F";
}

echo "Your grade is: $grade"; // B
?>

Important: PHP evaluates conditions top-to-bottom and enters the first matching block. Conditions are mutually exclusive — only one block executes.

Ternary operator

Compact if-else for simple assignments:

<?php
$age = 20;
$label = ($age >= 18) ? "Adult" : "Minor";
echo $label; // Adult
?>

Nested if

An if statement inside another if:

<?php
$age = 25;
$hasTicket = true;

if ($age >= 18) {
    if ($hasTicket) {
        echo "Welcome to the event!";
    } else {
        echo "You need a ticket.";
    }
} else {
    echo "Sorry, you must be 18+.";
}
?>

Tip: Deeply nested if statements are hard to read. Consider extracting conditions into variables or using early returns.

The match expression

PHP 8+ introduced match — a strict comparison alternative to switch:

<?php
$day = "Monday";

$result = match($day) {
    "Monday"    => "Start of the work week",
    "Friday"    => "Almost weekend!",
    "Saturday",
    "Sunday"    => "Weekend!",
    default     => "Midweek",
};

echo $result; // Start of the work week
?>

Key differences from switch:

<?php
// match uses strict comparison (===)
// switch uses loose comparison (==)

$value = "1";

match($value) {
    1 => "integer one",   // NO MATCH — "1" !== 1
    default => "default",
};

switch($value) {
    case 1:               // MATCHES — "1" == 1 is true
        echo "integer one";
        break;
}
?>

match also supports arrow functions for complex logic:

<?php
$statusCode = 404;

$message = match($statusCode) {
    200 => "OK",
    301 => "Moved Permanently",
    404 => "Not Found",
    500 => "Server Error",
    default => "Unknown status",
};

echo "$statusCode: $message"; // 404: Not Found
?>

Combined conditions

Use logical operators to combine multiple conditions:

<?php
$age = 25;
$income = 50000;

// AND: both must be true
if ($age >= 18 && $income >= 30000) {
    echo "You qualify for the premium card.";
}

// OR: at least one must be true
if ($age < 12 || $age > 65) {
    echo "You get a discounted ticket.";
}

// NOT: inverts the condition
if (!isset($_GET["page"])) {
    $page = 1;
}
?>

Null coalescing as if-else

Use ?? for null checks:

<?php
$username = $_POST["username"] ?? $_GET["username"] ?? "Anonymous";

// Equivalent to:
if (isset($_POST["username"])) {
    $username = $_POST["username"];
} elseif (isset($_GET["username"])) {
    $username = $_GET["username"];
} else {
    $username = "Anonymous";
}
?>

Best practices

<?php
// GOOD: Early returns reduce nesting
function getDiscount(float $price, bool $isMember): float {
    if ($isMember) {
        return $price * 0.9;
    }
    if ($price > 100) {
        return $price * 0.95;
    }
    return $price;
}

// AVOID: Deeply nested if-else
if ($a) {
    if ($b) {
        if ($c) {
            // Hard to follow
        }
    }
}
?>

Mini Practice

Write PHP code that:

1. Uses if-elseif-else to convert a numeric grade (0-100) to a letter grade
2. Uses the match expression to map HTTP status codes to messages
3. Combines conditions with && and ||
4. Uses the ternary operator for a simple conditional assignment

Up Next

In the next lesson, you'll learn about Loops — for, while, do-while, and foreach in PHP.