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PHP-I Jun 2021

TODO

  • Look up Internet access stats

Class Notes

Statistics

/home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/public
  • To access from that directory:
http://sandbox/NAME_OF_PROGRAM.php

Attributes can be used in PHP 8 in place of docblocks

<?php
/**
 * Adds two integers
 *
 * @param int $a
 * @param int $b
 * @return int $result
 */
function add(int $a, int $b) : int
{
	return $a + $b;
}

echo add(2,2);
echo "\n";

#[description("Adds two integers") ]
#[int(a) ]
#[int(b) ]
#[returns(a - b)]
function sub(int $a, int $b) : int
{
	return $a - $b;
}

echo sub(2,2);
echo "\n";

You can also use words for logicals:

// you can use words instead of symbols:
$foo = 10;
$bar = 5;
echo ($foo == 10 and $bar == 5); // 1

$foo = 5;
$bar = 10;
echo ($foo != $bar or $foo > $bar); // 1
echo ($foo != $bar xor $foo > $bar); // 1

Recommended: use shell_exec() instead of back tics

<?php
// this will go away:
echo `ls -lha`;

// recommended
echo shell_exec('ls -lha');

Flattening or "unpacking" arrays:

<?php
$abc = ['A','B','C'];
$def = ['D','E','F'];
// this ends up with 2 element, each a sub-array
$foo = [$abc, $def];
// this "flattens" the two arrays and you end with
// a single 1 dimensioned array
$bar = [...$abc, ...$def];
var_dump($foo, $bar);

"Packing" an array by using the variadics operator as in the function signature

<?php
// Argument packing
$foo = 10;
$bar = 5;
$baz = 99;

// this use of the variadics operator
// has the effect of "packing" the array
function sum(...$args){
	// if you allow for an unlimited # arguments
	// you need to write you function to account for that
    return array_sum($args);
}
echo sum($foo, $bar, $baz, 9999); // 15

Arrays auto-assign indices as the next highest value. The order of the indices has no bearing on the order elements are stored. Elements are stored in the order received.

<?php
$a[1] = 'A';
$a[3] = 'B';
$a[2] = 'C';
$a[6] = 'D';
$a[]  = 'E';
$a[4] = 'F';
$a[]  = 'G';

var_dump($a);

// output:
/*
home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/public/test.php:10:
array(7) {
  [1] =>
  string(1) "A"
  [3] =>
  string(1) "B"
  [2] =>
  string(1) "C"
  [6] =>
  string(1) "D"
  [7] =>
  string(1) "E"
  [4] =>
  string(1) "F"
  [8] =>
  string(1) "G"
}
 */

When assigning multi-dimensional arrays, if the values are known in advance, use this style:

<?php
// Build the crew
$mission = [
	'STS395' => [
		['firstName' => 'Mark', 'lastName' => 'Watney', 'specialty' => 'Botanist'],
		['firstName' => 'Melissa', 'lastName' => 'Lewis', 'specialty' => 'Commander'],
		['firstName' => 'Beth', 'lastName' => 'Johanssen', 'specialty' => 'Computer Specialist'],
	]
];

// Output all elements
print_r($mission);

When rendering numeric values, PHP defaults to decimal (i.e. base 10) If you want other formats, use one of these options:

  • NumberFormatter class
  • number_format() function
  • printf() family of functions (uses a format string)

HTTP Basics

All incoming data is suspect

  • Filter validate and sanitize all suspect data
  • Escape suspect data upon output
echo htmlspecialchars($name);
  • Usually the web server is configured to recognize PHP in certain directories
    • In the VM: the config files are here:
/etc/apache2/sites-available
/etc/apache2/sites-enabled

Control Structures

Use of null coalesce operator vs. ternary

<?php
// null coalesce operator
$id = $_GET['id'] ?? $_POST['id'] ?? $_SESSION['id'] ?? $_COOKIE['id'] ?? 0;

// same thing with nested ternary ops:
// in PHP 8 use of parentheses are mandatory
// NOT recommended!
$id = ((!empty($_GET['id']))
	? $_GET['id']
	: ((!empty($_POST['id']))
		? $_POST['id']
		: ((!empty($_SESSION['id']))
			? $_SESSION['id']
			: 0)));

Example of nested foreach() loops

<?php
$mission = [
    'STS395' => [
        ['firstName' => 'Fred', 'lastName' => 'Flintstone', 'specialty' => 'Caveman'],
        ['firstName' => 'Barney', 'lastName' => 'Rubble', 'specialty' => 'Caveman Assistant'],
    ],
    'STS396' => [
        ['firstName' => 'Mark', 'lastName' => 'Watney', 'specialty' => 'Botanist'],
        ['firstName' => 'Melissa', 'lastName' => 'Lewis', 'specialty' => 'Commander'],
        ['firstName' => 'Beth', 'lastName' => 'Johanssen', 'specialty' => 'Computer Specialist'],
    ],
];

foreach ($mission as $key => $value) {
	echo "Mission: $key\n";
	foreach ($value as $i => $entry) {
		echo $entry['firstName'] . ' ' . $entry['lastName'] . "\n";
	}
}

Example of unpacking an array into individual variables:

<?php
$mission = [
    'STS395' => [
        ['firstName' => 'Fred', 'lastName' => 'Flintstone', 'specialty' => 'Caveman'],
        ['firstName' => 'Barney', 'lastName' => 'Rubble', 'specialty' => 'Caveman Assistant'],
    ],
    'STS396' => [
        ['firstName' => 'Mark', 'lastName' => 'Watney', 'specialty' => 'Botanist'],
        ['firstName' => 'Melissa', 'lastName' => 'Lewis', 'specialty' => 'Commander'],
        ['firstName' => 'Beth', 'lastName' => 'Johanssen', 'specialty' => 'Computer Specialist'],
    ],
];

foreach ($mission as $key => $value) {
	echo "Mission: $key\n";
	foreach ($value as $i => list('firstName' => $first, 'lastName' => $last)) {
		echo $first . ' ' . $last . "\n";
	}
}

foreach ($mission as $key => $value) {
	echo "Mission: $key\n";
	foreach ($value as $i => $entry) {
		extract($entry);
		echo $firstName . ' ' . $lastName . "\n";
	}
}


$mission = [
    'STS395' => [
        ['Fred', 'Flintstone', 'Caveman'],
        ['Barney', 'Rubble', 'Caveman Assistant'],
    ],
    'STS396' => [
        ['Mark', 'Watney', 'Botanist'],
        ['Melissa', 'Lewis', 'Commander'],
        ['Beth', 'Johanssen', 'Computer Specialist'],
    ],
];

// unpack a numeric array in the foreach() directly
foreach ($mission as $key => $value) {
	echo "Mission: $key\n";
	foreach ($value as $i => list($first, $last, $specialty)) {
		echo "$first $last is a $specialty\n";
	}
}

// unpack a numeric array inside the foreach() loop
foreach ($mission as $key => $value) {
	echo "Mission: $key\n";
	foreach ($value as $i => $entry) {
		[$first, $last, $specialty] = $entry;
		echo "$first $last is a $specialty\n";
	}
}

Once the objective has been achieved: exit the loop. In this example, once an 'ERROR' has been found, we're done!

<?php
$messages = [
	'Operation succeeded',
	'ERROR 402',
	'Parse ERROR',
	'Everything OK',
];

$found = 0;
$search = 'ERROR';
foreach ($messages as $item) {
    // "str_contains()" is only available in PHP 8!
	if (str_contains($item, $search)) {
		$found++;
		break;
	}
}
echo ($found)
	? 'ERROR found'
	: 'All OK';
echo "\n";

You should provide a data type hint for functions with components that are sensitive to the wrong data type

  • Protects the function from abuse
  • Makes the real source of the error quite clear
function searchForError(array $messages) : int
{
	$found = 0;
	$search = 'ERROR';
	foreach ($messages as $item) {
		if (str_contains($item, $search)) {
			$found++;
			break;
		}
	}
	return $found;
}
$messages = [
	'Operation succeeded',
	'ERROR 402',
	'Parse ERROR',
	'Everything OK',
];

echo (searchForError('WHATEVER'))
	? 'ERROR found'
	: 'All OK';

Use declare(strict_types=1) to enforce all type hints for that file

<?php
// if the following line is omitted, the type-hint acts like a filter (type-cast)
declare(strict_types=1);
// Example of function using "type hinting"
function add(int $a, int $b) : int
{
	return $a + $b;
}

echo "The sum of 2 and 2 is " . add(2, 2) . "\n";
echo "The sum of 33.33 and 22.22 is " . add(33.33, 22.22) . "\n";

Nullable type: ?string === string|null

<?php
// union types were introduced in PHP 8

function get_full_name(string $first, string $last, string|null $middle = NULL)
{
	return ($middle) ? "$first $middle $last\n" : "$first $last\n";
}

echo get_full_name('Fred', 'Flintstone', 'John');
echo get_full_name('Barney', 'Rubble');

// prior to PHP 8, a hybrid type:
// ?string === string|null

function get_full_name2(string $first, string $last, ?string $middle = NULL)
{
	return ($middle) ? "$first $middle $last\n" : "$first $last\n";
}

echo get_full_name2('Fred', 'Flintstone', 'John');
echo get_full_name2('Barney', 'Rubble');

Union types can go overboard:

<?php
// a bit ridiculous:
function dump(int|float|string|bool|array|object $whatever)
{
	var_dump($whatever);
}

dump(new ArrayObject());
dump([1,2,3,4,5]);

// this makes more sense:
function dump2(mixed $whatever)
{
	var_dump($whatever);
}

dump(new ArrayObject());

// another example of ridiculous:
// dump(true|false|bool $yesNo) {}

Array navigation functions example with while() loop

<?php
$invoiceItems = [
  ['invoiceNumber' => 123, 'invoiceAmount' => 100],
  ['invoiceNumber' => 124, 'invoiceAmount' => 50],
  ['invoiceNumber' => 125, 'invoiceAmount' => 150],
  ['invoiceNumber' => 126, 'invoiceAmount' => 55],
];

$tax = 0.10;

while ($items = current($invoiceItems)) {
    $amountWithTax =  $items['invoiceAmount'] + ($items['invoiceAmount'] * $tax);
    echo 'invoice #' . $items['invoiceNumber'] . ' with invoice amount ' . $items['invoiceAmount'] . ' has the final amount of ' .  $amountWithTax . ' after adding the tax';
    echo "\n";
    next($invoiceItems);
}

You can also assign a reference to a single array element

<?php
$mission = [
    'STS395' => [
        ['firstName' => 'Fred', 'lastName' => 'Flintstone', 'specialty' => 'Caveman'],
        ['firstName' => 'Barney', 'lastName' => 'Rubble', 'specialty' => 'Caveman Assistant'],
    ],
    'STS396' => [
        ['firstName' => 'Mark', 'lastName' => 'Watney', 'specialty' => 'Botanist'],
        ['firstName' => 'Melissa', 'lastName' => 'Lewis', 'specialty' => 'Commander'],
        ['firstName' => 'Beth', 'lastName' => 'Johanssen', 'specialty' => 'Computer Specialist'],
    ],
];

$name = &$mission['STS395'][1]['firstName'];
$name = 'Betty';

var_dump($mission);

Example using pass-by-reference for validation

<?php
function validate(array $data, string &$err_msg) : bool
{
	$error = 0;
	// checks for only alpha characters
	if (!ctype_alpha($data['name'])) {
		$err_msg .= "Only letters are allowed in the name\n";
		$error++;
	}
	if (!filter_var($data['email'], FILTER_VALIDATE_EMAIL)) {
		$err_msg .= "Invalid email address\n";
		$error++;
	}
	return ($error === 0);
}

$data = [
	'name' => 12345,
	'email' => 'bad.email.address'
];
$message = '';
if (validate($data, $message)) {
	echo "All OK\n";
} else {
	echo $message;
}

Calling program for the Forms demo in VM:

<?php
// place this calling program into:
// /home/vagrant/Zend/workspaces/DefaultWorkspace/sandbox/public/form.php
// call from a browser: http://sandbox/form.php
$config = include __DIR__ . '/../../orderapp/config/config.php';
include __DIR__ . '/../../orderapp/src/Forms.php';
echo getForm($config, 'new_order', NULL);

Example of vprintf + printf()

<?php
$a = 5398;
printf('%016b', $a);
echo "\n";

$data =	[
	['Fred', 999.99, 'Caveman'],
	['Wilma', 888.88, 'Cavewoman'],
];

foreach ($data as $row)
	vprintf('Name: %12s : Amount %8.2f : Title: %12s' . "\n", $row);

Example of using substr() to extract a filename extension

<?php
$fn = 'whatever.php';
$allowed = ['jpg', 'png', 'gif'];
$ext = substr(trim($fn), -3);
echo (in_array($ext, $allowed)) ? 'Allowed' : 'Denied';
echo "\n";
// comes back as "Denied" because the extension is not on the allowed list

Sanitizing a filename

<?php
$alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
echo $alpha[0] . $alpha[2] . $alpha[4];

$path = '/home/vagrant//Zend/workspaces/DefaultWorkspace/sandbox/public';
$fn   = 'test.php';
// alternative syntax:
// if ($path[-1] === '/') {
if ($path[strlen($path) - 1] === '/') {
	$final = $path . $fn;
} else {
	$final = $path . '/' . $fn;
}
echo str_replace('//', '/', $final) . "\n";

Example of a callback tree that produces output in different formats

  • Uses anonymous functions
<?php
$arr = ['A' => 111,'B' => 222,'C' => 333];

$callbacks = [
	// arrow function works well here
	'json' => fn(array $data) => json_encode($data, JSON_PRETTY_PRINT),
	// needs multiple lines of code, so we use an anonymous function
	'html' => function (array $data) {
		$out = '<table>';
		foreach ($data as $key => $value)
			$out .= '<tr><th>' . $key . '</th><td>' . $value . '</td></tr>';
		$out .= '</table>';
		return $out; }
];

echo $callbacks['json']($arr);
echo "\n";
echo $callbacks['html']($arr);
echo "\n";

I/O

Example using fopen() and fgetcsv() to read a data file

<?php
// data source: https://download.geonames.org/export/dump/countryInfo.txt
$fn = '/home/vagrant/Downloads/countryInfo.txt';
$fh = fopen($fn, 'r');
$data = [];
while (!feof($fh)) {
	$temp = fgetcsv($fh, separator:"\t");
	if (empty($temp) || $temp[0][0] === '#') continue;
	$data[] = $temp;
}
var_dump($data);

Example accessing a remote website

<?php
$contents = file_get_contents('https://google.com');
$contents = str_ireplace('Google', 'Boogle', $contents);
echo $contents;

Example using file_get_contents() to post form data

<?php
$target   = 'http://' . $host . '/ch12/php8_chat_ajax.php';
$response = 'Default';
if ($_POST) {
    $user = $_POST['from'] ?? '';
    $_SESSION['user'] = $user;
    $headers = [
        'Accept: text/html',
        'Content-type: application/x-www-form-urlencoded',
    ];
    $opts = [
        'http' => [
            'method'  => 'POST',
            'header'  => implode("\r\n", $headers),
            'content' => http_build_query($_POST)
        ]
    ];
    $context = stream_context_create($opts);
    $response = file_get_contents($target, FALSE, $context);
    $data = json_decode($response, TRUE);
}

Example from labs

<?php
$name = 'data.txt';
$textArray = ['Some ', 'text', 'abc', 'jiofsjij'];
$file = fopen($name, 'w+');
foreach($textArray as $text) {
  fwrite($file, $text . "\n");
}
rewind($file);
// another approach
echo substr(fread($file, 4096), 2, 2);
fclose($file);
$contents = file($name);
var_dump($contents);

Getting a list of files in a directory

<?php
// single directory
$path = __DIR__;
$list = glob($path . '/*');
foreach ($list as $fn) echo $fn . "\n";

// or grab an entire directory tree
// see: https://php.net/SPL
$iter = new RecursiveDirectoryIterator($path);
$all  = new RecursiveIteratorIterator($iter);
// $obj === SplFileInfo instance
foreach ($all as $fn => $obj) echo $fn . "\n";

PHP Packages

Web Concepts

  • Use parse_url() to breakdown a URL into its parts
<?php
$url = 'https://mars-express.com/path/to/whatever?id=124&mission=STS395';
$parsed = parse_url($url);
var_dump($parsed);
// output
/*
 * array(4) {
  ["scheme"]=>
  string(5) "https"
  ["host"]=>
  string(16) "mars-express.com"
  ["path"]=>
  string(17) "/path/to/whatever"
  ["query"]=>
  string(21) "id=124&mission=STS395"
}
*/
  • Also use urlencode() for any data added to the base URL
<?php
$url = 'https://mars-express.com/path/to/whatever?';
echo $url . urlencode('status=Is this going to work?');

To see what's coming into your PHP program from HTTP:

<?php
phpinfo(INFO_VARIABLES);

Various form styles

  • Mainly HTML with PHP mixed in
  • Includes example of validating the name field
<?php
$days = ['Mon','Tue','Wed','Thu','Fri','Sat','Sun'];
$allowed = ['Mon','Tue','Wed','Thu','Fri'];
$error = 0;
$name = '';
$email = '';
$message = '';
$daySelect = '';
$dayCheck  = [];
if (!empty($_POST)) {
	// validate name
	$name = $_POST['name'] ?? '';
	if ($name) {
		if (strlen($name) > 16) {
			$message .= "Name must be 16 chars or less\n";
			$error++;
		}
		if (!ctype_alpha($name)) {
			$message .= "Name must have only letters\n";
			$error++;
		}
		// example of filtering
		$name = strip_tags($name);
	}
	// validate day_select
	$daySelect = $_POST['day_select'] ?? '';
	if (!in_array($daySelect, $allowed)) {
		$message .= "Day was not included in the set of allowed days\n";
		$error++;
	}
}
$message .= ($error === 0) ? "Form data is valid\n" : "Form data has errors\n";
?>
<form method="post">
Name: <input type="text" name="name" value="<?= htmlspecialchars($name) ?>" />
<br />Email: <input type="email" name="email" />
<br />Date: <input type="date" name="date" />
<br /><select name="day_select">
<?php foreach ($days as $day) echo '<option>' . $day . '</option>'; ?>
</select>
<br />
<?php
foreach ($days as $day) {
	echo '<input type="checkbox" name="day_check[]" value="' . $day . '" />' . $day . '&nbsp;';
}
?>
</select>
<br /><input type="submit" />
</form>
<?= nl2br($message); ?>
<?php phpinfo(INFO_VARIABLES); ?>

Example from file labs

<?php
// single directory
$path = __DIR__;
$list = glob($path . '/*');
echo '<table>';
echo '<tr><th>Name</th><th>Size in Bytes</th><th>Lines</th></tr>';
foreach ($list as $fn) {
	echo '<tr>';
	echo "<td>" . basename($fn) . "</td>";
	echo '<td>' . filesize($fn) . '</td>';
	$lines = count(file($fn)) - 1;
	echo "<td>$lines</td>";
	echo '</tr>';
}
echo "</table>\n";

Example of cookie usage:

Database Operations

Basic query example

<?php
$conn = mysqli_connect('localhost', 'vagrant', 'vagrant', 'phpcourse');
$result = mysqli_query($conn, 'SELECT * FROM customers');
$num_rows = mysqli_row_count($result);	// especially useful for INSERT, UPDATE and DELETE
// gives results 1 row at a time
// use this if you anticipate a large result set
while ($row = mysqli_fetch_array($result, MYSQLI_ASSOC)) {
	var_dump($row);
}


// gives you all rows at once
// use this is expected return is no more than 1000 to 2000 rows
// $data = mysqli_fetch_all($result, MYSQLI_ASSOC);

Miscellaneous

Highly recommended JavaScript library