5_logic-groups.php

<?php
// Chapter-5

// Question-1 

// 1. Write a function to return an HTML <img /> tag. 
// The function should accept a mandatory argument of the image URL and optional arguments for alt text, height, and width.

// Answer-1

function html_img($url, $alt = null, $height = null, $width = null)
{
    $html = '<img src="' . $url . '"';
    if (isset($alt)) {
        $html .= ' alt="' . $alt . '"';
    }
    if (isset($height)) {
        $html .= ' height="' . $height . '"';
    }
    if (isset($width)) {
        $html .= ' width="' . $width . '"';
    }
    $html .= '/>';
    return $html;
}

// Question-2

// 2. Modify the function in the previous exercise so that only the filename is passed to the function in the URL argument. 
// Inside the function, prepend a global variable to the filename to make the full URL. 
// For example, if you pass photo.png to the function, and the global variable contains /images/, 
// then the src attribute of the returned <img> tag would be /images/photo.png. 
// A function like this is an easy way to keep your image tags correct, even if the images move to a new path or server. 
// Just change the global variable—for example, from /images/ to http://images.example.com/.

// Answer-2

function html_img2($file, $alt = null, $height = null, $width = null)
{
    if (isset($GLOBALS['image_path'])) {
        $file = $GLOBALS['image_path'] . $file;
    }
    $html = '<img src="' . $file . '"';
    if (isset($alt)) {
        $html .= ' alt="' . $alt . '"';
    }
    if (isset($height)) {
        $html .= ' height="' . $height . '"';
    }
    if (isset($width)) {
        $html .= ' width="' . $width . '"';
    }
    $html .= '/>';
    return $html;
}


// Question-3

// 3. Put your function from the previous exercise in one file. 
// Then make another file that loads the first file and uses it to print out some <img /> tags.

// Answer-3

// The html_img2() function from the previous exercise is saved in this file
include "html-img2.php";
$image_path = '/images/';
print html_img2('puppy.png');
print html_img2('kitten.png', 'fuzzy');
print html_img2('dragon.png', null, 640, 480);

// Question-4

// 4. What does the following code print out? ?>
<?php
function restaurant_check($meal, $tax, $tip)
{
    $tax_amount = $meal * ($tax / 100);
    $tip_amount = $meal * ($tip / 100);
    return $meal + $tax_amount + $tip_amount;
}

$cash_on_hand = 31;
$meal = 25;
$tax = 10;
$tip = 10;

while (($cost = restaurant_check($meal, $tax, $tip)) < $cash_on_hand) {
    $tip++;
    print "I can afford a tip of $tip% ($cost)\n";
}
?><?php

// Answer-4

// I can afford a tip of 11% (30)
// I can afford a tip of 12% (30.25)
// I can afford a tip of 13% (30.5)
// I can afford a tip of 14% (30.75)

// Question-5

// 5. Web colors such as #ffffff and #cc3399 are made by concatenating the hexadecimal color values for red, green, and blue. 
// Write a function that accepts decimal red, green, and blue arguments and returns a string containing 
// the appropriate color for use in a web page. For example, if the arguments are 255, 0, and 255, 
// then the returned string should be #ff00ff. You may find it helpful to use the built-in function dechex(), 
// which is documented at http://www.php.net/dechex.

// Answer-5

/* Using dechex(): */
function web_color1($red, $green, $blue)
{
    $hex = [dechex($red), dechex($green), dechex($blue)];
    // Prepend a leading 0 if necessary to 1-digit hex values
    foreach ($hex as $i => $val) {
        if (strlen($i) == 1) {
            $hex[$i] = "0$val";
        }
    }
    return '#' . implode(
        ''
        ,
        $hex
    );
}
/* You can also rely on sprintf()'s %x format character to do hex-to-decimal conversion: */
function web_color2($red, $green, $blue)
{
    return sprintf('#%02x%02x%02x', $red, $green, $blue);
}