# Control structures

# Selection

In PHP, you can use the following (classical) selection structures
- if
- if else
- if elseif
- switch
- match (PHP 8+)
Open course/selection.php
- Change the value of $scorePHP (interesting values: 4, 15, 12.7, 25.4, null) to see the effect on the different selection structures

<article>
    <?php
    $scorePHP = 9;
    echo "<p> \$scorePHP = $scorePHP </p>\n";
    ?>
</article>

<article>
    <h2>if</h2>
    <?php
    if ($scorePHP >= 10) {
        echo "<p> You passed the PHP course. Congratulations! </p>\n";
    }
    ?>
</article>

<article>
    <h2>if else</h2>
    <?php
    if ($scorePHP >= 10) {
        echo "<p> You passed the PHP course. Congratulations! </p>\n";
    } else {
        echo "<p> Unfortunately, you failed the PHP course. Better luck next time! </p>\n";
    }
    ?>
</article>

<article>
    <h2>Ternary operator</h2>
    <?php
    echo $scorePHP >= 10 ? "<p> You passed the PHP course. Congratulations! </p>\n" : "<p> Unfortunately, you failed the PHP course. Better luck next time! </p>\n";
    ?>

</article>

<article>
    <h2>if elseif</h2>
    <?php
    if ($scorePHP >= 10) {
        echo "<p> You passed the PHP course. Congratulations!</p>\n";
    } elseif ($scorePHP >= 8) {
        echo "<p> You failed the PHP course, but you may tolerate it! </p>\n";
    } else {
        echo "<p> Unfortunately, you failed the PHP course. Better luck next time! </p>\n";
    }
    ?>
</article>

<article>
    <h2>switch</h2>
    <?php
    switch ($scorePHP) {
        case 0:
        case 1:
        case 2:
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
            echo "<p> Unfortunately, you failed the PHP course. Better luck next time!  </p>\n";
            break;
        case 8:
        case 9:
            echo "<p> You failed the PHP course, but you may tolerate it! </p>\n";
            break;
        case 10:
        case 11:
        case 12:
        case 13:
        case 14:
        case 15:
        case 16:
        case 17:
        case 18:
        case 19:
        case 20:
            echo "<p> You passed the PHP course. Congratulations!</p>\n";
            break;
        default:
            echo "<p> -- INVALID SCORE -- </p>\n";
    }
    ?>
</article>

<article>
    <h2>match</h2>
    <?php
    $result = match ($scorePHP) {
        0, 1, 2, 3, 4, 5, 6, 7 => 'Unfortunately, you failed the PHP course. Better luck next time!',
        8, 9 => 'You failed the PHP course, but you may tolerate it!',
        10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 => 'You passed the PHP course. Congratulations!',
        default => '-- INVALID SCORE --',
    };
    echo "<p> $result </p>\n";
    ?>
</article>

<article>
    <h2>Null coalescing operator</h2>
    <?php
    echo "<p> Your score for PHP = " . ($scorePHP ?? '-- NO SCORE AVAILABLE --') . "</p>\n";
    ?>
</article>

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The match expression is 'almost' similar to a switch statement.
- Unlike switch, it will evaluate to a value much like ternary expressions.
- Unlike switch, the comparison is an identity check (===) rather than a weak equality check (==)
The ternary operator condition ? 'valueTrue' : 'valueFalse' provides a shorthand for an if else statement.
- If the condition evaluates to true, the result of the operator is 'valueTrue'.
- Otherwise (condition evaluates to false), the result of the operator is 'valueFalse'.
During coding, one often has to check whether a $variable exists (and is not null). This can be achieved by the PHP isset() function in combination with a ternary operator: isset($variable) ? $variable : 'fallback'. The null coalescing operator $variable ?? 'fallback' can be used as a shorthand for the latter statement.

# Iteration

In PHP, you can use the following (classical) iteration structures
- for
- while
- do while
Open course/iteration.php
- Change the values of $base and/or $depthMultiplicationTable (interesting value: 0) to see the effect on the different iteration structures

<article>
    <?php
    $base = 7;
    $depthMultiplicationTable = 10;
    echo "<p> \$base = $base </p>\n";
    echo "<p> \$depthMultiplicationTable = $depthMultiplicationTable </p>\n"
    ?>
</article>

<article class="grid sm:grid-cols-3 gap-4">
    <section>
        <h2>for</h2>
        <ul>
        <?php
        for ($i = 1; $i <= $depthMultiplicationTable; $i++) {
            echo "<li> $i x $base = " . ($i * $base) . "</li>\n";
        }
        ?>
        </ul>
    </section>
    <section>
        <h2>while</h2>
        <ul>
        <?php
        $j = 1;
        while ($j <= $depthMultiplicationTable) {
            echo "<li> $j x $base = " . ($j * $base) . "</li>\n";
            $j++;
        }
        ?>
        </ul>
    </section>
    <section>
        <h2>do while</h2>
        <ul>
        <?php
        $k = 1;
        do {
            echo "<li> $k x $base = " . ($k * $base) . "</li>\n";
            $k++;
        } while ($k <= $depthMultiplicationTable);
        ?>
        </ul>
    </section>
</article>

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