PHP Zero to Advanced #3: Conditionals, Loops & the match Expression

So far our scripts have run from top to bottom, one line after another. Real programs need to make decisions ("is this user logged in?") and repeat work ("send an email to every subscriber"). In this part you will learn PHP's control structures: if, switch, the modern match expression, and all the loop types.

if, elseif, and else

The if statement runs a block only when its condition is truthy. Chain extra conditions with elseif and catch everything else with else. Conditions are checked from top to bottom, and only the first matching block runs.

<?php

$score = 82;

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

echo "Score $score gets grade $grade\n";

$age = 17;
$hasPermission = true;

if ($age >= 18 || $hasPermission) {
    echo "Access granted\n";
}

Output:

Score 82 gets grade B
Access granted

Combine conditions with && (and), || (or), and ! (not). Always use curly braces, even for one-line blocks; it prevents bugs when you add more lines later.

Ternary, short ternary, and null coalescing

For simple "pick one of two values" decisions, the inline operators are shorter and still readable:

<?php

$stock = 0;
echo $stock > 0 ? "In stock" : "Sold out", "\n";

$nickname = "";
echo $nickname ?: "Anonymous", "\n";      // short ternary: falsy check

$settings = ['theme' => null];
echo $settings['theme'] ?? "light", "\n"; // null coalescing: null/undefined check
echo $settings['lang'] ?? "en", "\n";

Output:

Sold out
Anonymous
light
en

The difference matters: ?: falls back on any falsy value (including "" and 0), while ?? only falls back on null or a missing key, and it never raises a warning for undefined keys.

switch

switch compares one value against many cases. Each case needs a break, otherwise execution "falls through" to the next case. Sometimes fall-through is intentional, as with the weekend example below.

<?php

$day = "sat";

switch ($day) {
    case "sat":
    case "sun":
        echo "Weekend\n";
        break;
    case "fri":
        echo "Almost weekend\n";
        break;
    default:
        echo "Weekday\n";
}

Output:

Weekend

switch uses loose comparison (==), which is one reason modern PHP code often prefers match.

The match Expression (PHP 8)

match is like a safer, more compact switch:

• It is an expression, so it returns a value you can assign or echo.
• It uses strict comparison (===).
• There is no fall-through and no break needed.
• Multiple values can share one arm, separated by commas.

<?php

$status = 404;

$message = match ($status) {
    200, 201 => "Success",
    301, 302 => "Redirect",
    404 => "Not Found",
    500 => "Server Error",
    default => "Unknown",
};

echo $message . "\n";

$score = 82;
$grade = match (true) {
    $score >= 90 => "A",
    $score >= 80 => "B",
    $score >= 70 => "C",
    default => "D",
};

echo "Grade: $grade\n";

Output:

Not Found
Grade: B

The match (true) pattern is a neat replacement for long if/elseif chains that only assign a value. Because match is strict, 1 and "1" are different, and if no arm matches and there is no default, PHP throws an UnhandledMatchError:

<?php

$value = "1";

echo match ($value) {
    1 => "Integer one",
    "1" => "String one",
};
echo "\n";

try {
    echo match ("2") {
        "1" => "One",
    };
} catch (\UnhandledMatchError $e) {
    echo get_class($e) . ": " . $e->getMessage() . "\n";
}

Output:

String one
UnhandledMatchError: Unhandled match case '2'

We will cover try/catch properly in Part 8. For now, remember: add a default arm unless you really want an error for unexpected values.

Loops

for

Use for when you know how many times to loop. It has three parts: initialization, condition, and step.

<?php

for ($i = 1; $i <= 5; $i++) {
    echo "Row $i\n";
}

for ($i = 10; $i > 0; $i -= 3) {
    echo $i . " ";
}
echo "\n";

Output:

Row 1
Row 2
Row 3
Row 4
Row 5
10 7 4 1 

while and do-while

while keeps going as long as the condition is true, which is ideal when you do not know the number of iterations in advance. do-while checks the condition after the body, so it always runs at least once.

<?php

$balance = 1000;
$months = 0;

while ($balance < 1500) {
    $balance *= 1.1;   // 10% growth per month
    $months++;
}

echo "Target reached after $months months: " . round($balance, 2) . "\n";

$attempt = 0;
do {
    $attempt++;
    echo "Attempt #$attempt\n";
} while ($attempt < 3);

Output:

Target reached after 5 months: 1610.51
Attempt #1
Attempt #2
Attempt #3

foreach

foreach is the loop you will use most in PHP, because it iterates over arrays directly. You can get just the values, or both the keys and the values.

<?php

$fruits = ["apple", "banana", "mango"];

foreach ($fruits as $fruit) {
    echo "- $fruit\n";
}

$prices = ["apple" => 5000, "banana" => 3000, "mango" => 12000];

foreach ($prices as $name => $price) {
    echo str_pad($name, 8) . number_format($price, 0, ',', '.') . "\n";
}

Output:

- apple
- banana
- mango
apple   5.000
banana  3.000
mango   12.000

break and continue

continue skips to the next iteration, and break exits the loop completely.

<?php

for ($i = 1; $i <= 10; $i++) {
    if ($i % 2 === 0) {
        continue;   // skip even numbers
    }
    if ($i > 7) {
        break;      // stop the loop entirely
    }
    echo $i . " ";
}
echo "\n";

Output:

1 3 5 7 

Loops can also be nested. Here is a small multiplication table:

<?php

for ($row = 1; $row <= 3; $row++) {
    for ($col = 1; $col <= 3; $col++) {
        echo str_pad($row * $col, 4, " ", STR_PAD_LEFT);
    }
    echo "\n";
}

Output:

   1   2   3
   2   4   6
   3   6   9

Common Mistakes

• Using = instead of ==/=== in a condition. if ($role = "admin") assigns the value and is always true.
• Forgetting break in switch. The next case runs too. Prefer match when you are mapping values.
• Infinite loops. Make sure the while condition eventually becomes false, for example by updating the counter.
• Foreach by reference without unset. After foreach ($arr as &$v), $v still points to the last element. A later loop using $v silently overwrites it:

<?php

$numbers = [1, 2, 3];

foreach ($numbers as &$n) {
    $n *= 2;
}
// unset($n);  <-- forgetting this causes the bug below

foreach ($numbers as $n) {
}

print_r($numbers);

Output:

Array
(
    [0] => 2
    [1] => 4
    [2] => 4
)

The last element became 4 instead of 6. Always call unset($n) right after a by-reference loop, or avoid references and build a new array instead.

Exercise: FizzBuzz

Print the numbers 1 to 15. For multiples of 3 print "Fizz", for multiples of 5 print "Buzz", and for multiples of both print "FizzBuzz". Try it yourself first, then compare with this match (true) solution:

<?php

for ($i = 1; $i <= 15; $i++) {
    echo match (true) {
        $i % 15 === 0 => "FizzBuzz",
        $i % 3 === 0 => "Fizz",
        $i % 5 === 0 => "Buzz",
        default => $i,
    }, "\n";
}

Output:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz

Notice that the order of the arms matters: the % 15 check must come first, because match stops at the first arm that matches.

Summary

• if/elseif/else handles general branching; ternary and ?? handle quick value choices.
• switch uses loose comparison and needs break; match is strict, returns a value, and has no fall-through.
• Use for for counted loops, while/do-while for condition-based loops, and foreach for arrays.
• break exits a loop, continue skips to the next iteration.

In Part 4 we will organize code into reusable functions with type declarations, default parameters, arrow functions, and a clear understanding of variable scope.