ฟังชั่น

    <?php

    function function_name($parameter) {
        // code
    }

    <?php

    function stand_up() {
        echo 'Please stand up!';
    }

    stand_up();
    // print: Please stand up!

    <?php

    // By value function
    function double($num) {
        echo 'Double value of ' . $num . ' is ';
        $num = $num * 2;
        echo $num;
    }
    // By reference function
    function half(&$num) {
        echo 'Half value of ' . $num . ' is ';
        $num = $num / 2;
        echo $num;
    }

    $x = 50;

    double($x);
    // print: Double value of 50 is 100
    echo $x;
    // print: 50

    half($x);
    // print: Half value of 50 is 25
    echo $x;
    // print: 25

    <?php

    function vat_include($prize, $vat = 7) {
        $total = $prize + (($prize * $vat) / 100);
        echo 'Payment: ' . $total;
    }

    // use default vat = 7%
    vat_include(200);
    // print: Payment: 214

    // use custom vat = 10%
    vat_include(1000, 10);
    //print: Payment: 1100

    <?php

    function power_up($num) {
        return $num * $num;
    }

    $pow = power_up(20);
    // $pow = 400

    <?php

    function divide_func($base, $divider) {
        if (0 == $divide) {
            echo 'Cannot divide by zero';
            return;
        }
        $result = $base / $divider;
        echo 'Result is ' . $result;
    }