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PHP Certification - Dec 2022

REMEMBER: send C.T. the updated version

Homework

For Fri 09 Dec

  • All remaining quiz questions
  • Final mock exam

For Wed 07 Dec

  • Quiz questions for "OOP" topic
  • Mock Exam #2

For Mon 05 Dec

  • Quiz questions for "Arrays" topic
  • Quiz questions for "I/O" topic
  • Quiz questions for "Functions" topic
  • Mock Exam #1 (to be uploaded in class via Zoom)

For Fri 02 Dec

  • Quiz questions for "Basics" topic
  • Quiz questions for "Data Formats and Types" topic
  • Quiz questions for "Strings and Patterns" topic

TODO

Docker Container Setup

  • Download the ZIP file via Zoom
  • Unzip into a new folder /path/to/zip
  • Follow the setup instructions in /path/to/zip/README.md

Class Notes

Basics

Classnames are not case sensitive, even when using namespaces:

<?php
namespace X {
        class Test
        {
                public $name = 'X_TEST';
        }
}

namespace Y {
        class TEST
        {
                public $name = 'Y_TEST';
        }
}

namespace {
        use X\Test;
        use Y\TEST;;
        // solution: use an alias:
        // use Y\TEST as YTest;
        $test = new Test();
        echo $test->name;
}
// output:
// PHP Fatal error:  Cannot use Y\TEST as TEST because the name is already in use in /srv/code/test.php on line 18

What's the difference between define() and const for constants:

<?php
namespace x {
        define('TEST1', 'xyz');
        const TEST2 = 'abc';
}

namespace y {

        function test()
        {
                return TEST1 . TEST2;
        }

        echo test();
        // output: xyzTEST2
}

Namespaces:

  • Cannot have keywords in the namespace in PHP 7.1
namespace Test\List\Whatever;

use ArrayObject;

$obj = new ArrayObject([1,2,3,4,5]);
var_dump($obj);
// PHP Parse error:  syntax error, unexpected 'List' (T_LIST), expecting identifier (T_STRING) in /srv/code/test.php on line 2

IMPORTANT: when assigning objects, it's automatically by reference (even without the &)

<?php
$obj = new stdClass();
$obj->name = 'TEST';
$abc = $obj;
$abc->name = 'Whatever';
echo $obj->name;
echo PHP_EOL;
// Output: "Whatever"

What is considered "empty"?

<?php
namespace abc {
        define('WHATEVER', 'Whatever', TRUE);
        const ANYTHING = 'Anything';
}

namespace xyz {
        echo WHATEVER;
        echo ANYTHING;
}

Bitwise Operators

Tutorial oriented towards the exam:

<?php
echo "Logical AND\n";
printf("%04b\n", 0b00 & 0b00);  // 0
printf("%04b\n", 0b00 & 0b01);  // 0
printf("%04b\n", 0b01 & 0b00);  // 0
printf("%04b\n", 0b01 & 0b01);  // 1

echo "Logical OR\n";
printf("%04b\n", 0b00 | 0b00);  // 0
printf("%04b\n", 0b00 | 0b01);  // 1
printf("%04b\n", 0b01 | 0b00);  // 1
printf("%04b\n", 0b01 | 0b01);  // 1

echo "Logical XOR\n";
printf("%04b\n", 0b00 ^ 0b00);  // 0
printf("%04b\n", 0b00 ^ 0b01);  // 1
printf("%04b\n", 0b01 ^ 0b00);  // 1
printf("%04b\n", 0b01 ^ 0b01);  // 0

Examples of the three ops:

<?php
$a = 0b11111111;
$b = 0b11011101;

printf("%08b", $a & $b); // 1101 1101
printf("%08b", $a | $b); // 1111 1111
printf("%08b", $a ^ $b); // 0010 0010

Left/right shift illustration:

<?php
echo 16 << 3;
echo "\n";
echo 0b10000000;
echo "\n";

echo 16 >> 3;
echo "\n";
echo 0b00000010;
echo "\n";

echo 15 >> 3;
echo "\n";
echo 0b00000001;
echo "\n";

Comparing ASCII values

<?php
$a = 'A';
$b = 'b';
var_dump($a < $b);      // TRUE
var_dump($a == $b);     // FALSE
var_dump($a > $b);      // FALSE

Nested Ternary Construct

$a = 30;
$b = 20;
echo ($a < $b) ? 'Less' : (($a == $b) ? 'Equal' : 'Greater');
// output: "Greater"

Null coalesce operator example

$token = $_GET['token'] ?? $_POST['token'] ?? $_COOKIE['token'] ?? 'DEFAULT';

php.ini file settings:

<?php
$a = '123';

switch ($a) {
        case 123 :
                echo __LINE__;
        case 456 :
                echo __LINE__;
        case '123' :
                echo __LINE__;
        default :
                echo __LINE__;
}
echo PHP_EOL;

// expected: 6
// actual:   681012

continue and break

Garbage Collection

Data Formats

Read up on SimpleXMLElement

<?php
$str = <<<EOT
<Outer>
        <A>
                <B>
                        <C>Value 1</C>
                        <C>Value 2</C>
                        <C>Value 3</C>
                        <C id="123" />
                </B>
                <B>
                        <C>Value 4</C>
                        <C>Value 5</C>
                        <C>Value 6</C>
                </B>
        </A>
        <A>
                <C>Value 2-1</C>
                <C>Value 2-2</C>
                <C>Value 2-3</C>
                <C id="123" />
        </A>
</Outer>
EOT;
$xml = new SimpleXMLElement($str);
echo $xml->A->B->C[3]['id']; // output: "123"
echo PHP_EOL;
echo $xml->A[1]->B->C; // output: "Value 2-1"
echo PHP_EOL;
var_dump($xml->xpath('//A/C')); // returns array of 4 SimpleXMLElement instances for the "C" nodes directly under "A"
echo PHP_EOL;

Don't forget that to run a SOAP request, you can also use:

<?php
$arr = [
        'A' => [
                'B' => [
                        'C' => [
                                'C1',
                                'C2',
                                'C3',
                                'D' => [
                                        'E' => [
                                                'E1',
                                                'E2',
                                                'E3',
                                        ],
                                ],
                        ],
                ],
        ],
];

$json = json_encode($arr, JSON_PRETTY_PRINT, 512);
$decoded[] = json_decode($json, FALSE); // stdClass instance
$decoded[] = json_decode($json, TRUE);  // associative array
var_dump($decoded);
echo PHP_EOL;
  • DateTime examples
<?php
// for relative formats see:
// https://www.php.net/manual/en/datetime.formats.relative.php
$date[] = new DateTime('third thursday of next month');
$date[] = new DateTime('now', new DateTimeZone('CET'));
$date[] = new DateTime('@' . time());
$date[] = (new DateTime())->add(new DateInterval('P3D'));
var_dump($date);

Example from slides:

<?php

$date = new DateTime();
// DateTime::COOKIE = "1, d-M-y H:i:s T"
echo $date->format(DateTime::COOKIE);
echo PHP_EOL;

// DateTime::RSS = "D, d M Y H:i:s O"
echo $date->format(DateTime::RSS);
echo PHP_EOL;

DateTime examples:

Study on DateTimeInterval and DateTimeZone and also "relative" time formats

Strings

  • Be very careful with strpos() and stripos()
<?php
$str = 'The quick brown fox jumped over the fence';
echo '"The" was ';
echo (stripos($str, 'The')) ? 'found' : 'not found';
echo ' in the string ' . $str;
echo PHP_EOL;

// actual output:
// "The" was not found in the string The quick brown fox jumped over the fence
  • Study substr() with negative args
<?php
$a = 'test.php';
//   test.               php
$b = substr($a, 0, -3) . substr($a, -3);
echo ($a === $b) ? 'T' : 'F';

// ouput: "T"
  • Study the docs on sprintf() to get format codes for that family of functions
  • Example using negative offsets:
<?php
$dir = '/home/doug/some/directory/';
if (substr($dir, 0, 1) === '/') echo 'Leading slash' . PHP_EOL;
if (substr($dir, -1) === '/') echo 'Trailing slash' . PHP_EOL;
if ($dir[-1] === '/') echo 'Trailing slash' . PHP_EOL;

Phonetic functions example:

<?php
$a = 'akshual';
$b = 'actual';
echo metaphone($a);     // AKXL
echo PHP_EOL;
echo metaphone($b); // AKTL
echo PHP_EOL;


<?php
$text = 'Doug Bierer';
$patt = '/(.*)\s(.*)/';
echo preg_replace($patt, '$2, $1', $text);
  • preg_replace() and preg_match() example using sub-patterns:
<?php
$string = 'April 15, 2003';
$pattern = '/(\w+) (\d+), (\d+)/i';
$replacement = '$2 $1 $3';
echo preg_replace($pattern, $replacement, $string);

preg_match($pattern, $string, $matches);
var_dump($matches);
  • Same thing, but going from European date format to American
<?php
$str = '5 April 2022';
$pat = '/^(\d+?) (\w+?) (\d{4})$/';
$rep = '$2 $1, $3';
echo preg_replace($pat, $rep, $str);
echo PHP_EOL;

Greediness Example:

<?php
$str = '<p>Para 1</p><p>Para 2</p><p>Para 3</p>';
// $pat = '!<p>.*</p>!';        // returns the entire string
$pat = '!<p>.*?</p>!';  // returns "<p>Para 1</p>"
preg_match($pat, $str, $matches);
var_dump($matches);
echo PHP_EOL;

Regex examples:

Arrays

For iterating through an array beginning-to-end don't forget about these functions:

  • array_walk()
  • array_walk_recursive()
  • array_map() Also: please don't forget the array navigation functions:
  • reset(): sets pointer to top
  • end() : sets pointer to end
  • prev() : advances array pointer
  • next() : un-advances array pointer
  • key() : returns index value at array pointer
  • current() : returns value of element at array pointer

I/O

Streams

  • Don't have to study all functions, just certain of the more common ones
  • https://www.php.net/streams
    • stream_context_create()
    • stream_wrapper_register()
    • stream_filter_register()
    • stream_filter_append()
    • stream_socket_client() In addition to the informational file functions mentioned, you also have:
  • fileatime()
  • filemtime()
  • filectime() etc.

Functions

OOP

  • Read up on magic methods!
  • Iteration
    • Lookup these interfaces and understand what they do
      • Traversable
        • Both of the interfaces mentioned extend this interface
      • Iterator
        • Introduced earlier
        • Requires hard-coded iteration methods
      • IteratorAggregate
        • Passes the buck
        • Don't have to hard code iteration methods
  • Inheritance
    • Visibility can go from protected in the super class to public in the sub-class, but not the other way around
    • Data types can go from specific to general, but not the other way around
<?php
class A
{
        protected $test = NULL;
        public function getTest()
        {
                return var_export($this->test, TRUE);
        }
        public function setTest(array $test)
        {
                $this->test = $test;
        }
}

class B extends A
{
        // doesn't work:
        // protected function setTest(ArrayIterator $test)

        // works:
        public function setTest(iterable $test)
        {
                $this->test = $test;
        }
}

$b = new B();
$b->setTest(new ArrayIterator([1,2,3]));
echo $b->getTest();
  • Abstract classes:
<?php
abstract class A
{
        protected $test = NULL;
        public function getTest()
        {
                return var_export($this->test, TRUE);
        }
        public abstract function setTest(array $test);
}

class B extends A
{
        public function setTest(iterable $test)
        {
                $this->test = $test;
        }
}

$b = new B();
$b->setTest(new ArrayIterator([1,2,3]));
echo $b->getTest();
  • Interface example
<?php
interface TestInterface
{
        public function setTest(array $test);
}

abstract class A implements TestInterface
{
        protected $test = NULL;
        public function getTest()
        {
                return var_export($this->test, TRUE);
        }
}

class B extends A
{
        // NOTE: this is mandatory as "setTest()" isn't defined anywhere else
        public function setTest(iterable $test)
        {
                $this->test = $test;
        }
}

$b = new B();
 $b->setTest(new ArrayIterator([1,2,3]));
echo $b->getTest();
  • Example that shows how classes implementing interfaces that extend from "Traversable" work as arguments
<?php
class ShowSomething
{
    public function show(Traversable $iterator)
    {
        $output = '<ul>';
        foreach ($iterator as $item)
            $output .= '<li>' . $item . '</li>';
        $output .= '</ul>' . PHP_EOL;;
        return $output;
    }
}
$show = new ShowSomething();

// this works because "ArrayIterator" implements "Iterator"
$obj  = new ArrayIterator(['A','B','C']);
echo $show->show($obj);

// this works because "ArrayObject" implements "IteratorAggregate"
$obj  = new ArrayObject(['A','B','C']);
echo $show->show($obj);
  • Magic method __invoke() example + examples of callable type
<?php
// list of "callable" variations
class Test
{
        public function something()
        {
                return 'SOMETHING';
        }
        public static function somethingElse()
        {
                return 'SOMETHING ELSE';
        }
}

function whatever ()
{
        return 'WHATEVER';
}

$what = function () {
        return 'WHAT';
};

$invoke = new class () {
        public function __invoke()
        {
                return 'INVOKE';
        }
};

function test (callable $callback)
{
        echo $callback();
        echo PHP_EOL;
}

$test = new Test();

// all of these are considered "callable"
test('whatever');
test($what);
test([$test, 'something']);
test('Test::somethingElse');
test($invoke);

<?php
class Test
{
        public $a = 0;
        public $b = 0;
    public $c = 'Test';
    public $d = [];
    public $e = '';
        public function __construct(int $a, float $b, string $c, array $d)
        {
                $this->a = $a;
                $this->b = $b;
                $this->c = $c;
                $this->d = $d;
                $this->e = md5(rand(1111,9999));
        }
        public function __sleep()
        {
                return ['a','b','c','d'];
        }
        public function __wakeup()
        {
                $this->e = md5(rand(1111,9999));
        }
}
$test = new Test(222, 3.456, 'TEST', [1,2,3]);
var_dump($test);
$str = serialize($test);
echo $str . PHP_EOL;

$obj = unserialize($str);
var_dump($obj);
  • SPL
    • Make sure you study:
      • *Iterator* : just know what they are
      • ArrayIterator and ArrayObject make sure you're up to speed on these!
    • Just be aware of the "classic" data structure classes
  • ArrayObject usage
<?php

$arrayobject = new ArrayObject(['one', 'two', 'three']);

$arrayobject[] = 'four';
$arrayobject[0] = '1';
$arrayobject->append('five');
$arrayobject['test'] = 'TEST';

// Iterate
foreach($arrayobject as $item) {
    echo $item . PHP_EOL;
}

// Iterate with injected ArrayIterator
$iterator = $arrayobject->getIterator();
while($iterator->valid()) {
    echo $iterator->key() . '=>' . $iterator->current();
    $iterator->next();
}

Database Topic

Fetch Modes:

  • Focus on array and object fetch modes Study the difference between bindValue() and bindParam()

Security Topic

Questions are drawn from here:

Web Features

Make sure you're up on the php.ini settings pertaining to web features URL: https://www.php.net/manual/en/ini.list.php

  • variables_order
  • request_order
  • memory_limit
  • post_max_size
  • upload_max_filesize
  • file_uploads
  • max_file_uploads

When the question refers to an "image button", here's what they mean:

<input type="image" src="image.gif" name="sub" />

Error Handling

Example of aggregated Catch block:

try {
    $pdo = new PDO($params);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException | Exception $e) {
    error_log('Database error: ' . date('Y-m-d H:i:s'));
} catch (Throwable $e) {
    error_log('Any and all errors or exceptions: ' . date('Y-m-d H:i:s'));
} finally {
    echo 'Database connection ';
    echo ($pdo) ? 'succeeded' : 'failed';
}

Example where an error isn't caught because the code never ran

  • The parsing process failed
  • The code never runs
  • No errors are thrown:
try {
        echo 'This won\'t work'
} catch (Throwable $t) {
        echo __LINE__ . "\n";
        echo get_class($t) . $t;
}

// actual output:
// PHP Parse error:  syntax error, unexpected '}', expecting ',' or ';' in /srv/code/test.php on line 4

In this example, the ParseError is caught be we're using eval() to evaluate code at runtime

  • ParseError can also be caught when using include() or require()
<?php
try {
        eval("echo 'This won\'t work' echo 'Because there's no semi-colon';");
} catch (Throwable $t) {
        echo __LINE__ . "\n";
        echo get_class($t) . $t;
}

// actual output:
/*
5
ParseErrorParseError: syntax error, unexpected 'echo' (T_ECHO), expecting ',' or ';' in /srv/code/test.php(3) : eval()'d code:1
Stack trace:
#0 {main}
#
*/

Example of making object callable:

<?php
$sum = new class () {
    public $num = 0;
    public function __invoke($val) {
        $this->num += $val;
    }
};

$a = [1, 2, 3, 4, 5, 6, 7, 8];
array_walk($a, $sum);
echo 'Sum of Digits: ' . $sum->num;
// output: 36

See: https://github.com/dbierer/classic_php_examples/blob/master/oop/callable_examples.php

Error Handling

Resources

Change Request

<?php
class UserEntity {
    public $hash = '';
    protected $first = '';
    protected $last  = '';
    public function __construct(string $first, string $last) {
        $this->first = $first;
        $this->last  = $last;
        $this->hash  = bin2hex(random_bytes(8));
    }
    public function __sleep() {
        return ['first','last'];
    }
    public function getFullName() {
        return $this->first . ' ' . $this->last;
    }
}
$userEntity = new UserEntity('Mark', 'Watney');
$str = serialize($userEntity);
echo $str;  // NOTE: "hash" does not appear in serialized string

<?php
class ServiceContainer {
    protected $services = [];
    public function __construct(string $name, callable $value){
        $this->set($name, $value);
    }
    public function set(string $name, callable $value) {
        $this->services[$name] = $value;
    }
    public function get(string $name) {
        return $this->services[$name]();
    }
}
$callback = function () { return (new DateTime())->format('l, d M Y'); };
$container = new ServiceContainer('date', $callback);
echo $container->get('date');

<?php
class UserEntity {
    public $hash = '';
    protected $first = '';
    protected $last  = '';
    public function __construct(string $first, string $last) {
        $this->first = $first;
        $this->last  = $last;
        $this->hash  = bin2hex(random_bytes(8));
    }
    public function __sleep() {
        return ['first','last'];
    }
    public function getFullName() {
        return $this->first . ' ' . $this->last;
    }
}
$userEntity = new UserEntity('Mark', 'Watney');
$str = serialize($userEntity);
echo $str;
echo PHP_EOL;