Data Types In PHP

DATA TYPES IN PHP

MARK NIEBERGALL

https://joind.in/talk/6d7f9

ABOUT MARK NIEBERGALL

DATA TYPES IN PHP

• PHP since 2005 • Masters degree in MIS • Senior Software Engineer • Team Lead • Drug screening project • President of Utah PHP User Group (UPHPU) • SSCP, CSSLP Certified and SME for (ISC)2 • PHP, databases, JavaScript • Drones, fishing, skiing, father, husband

ABOUT MARK NIEBERGALL

DATA TYPES IN PHP

ABOUT MARK NIEBERGALL

DATA TYPES IN PHP

UPHPU

DATA TYPES IN PHP

• Third Thursday of each month at 7pm • Venue is Vivint in Lehi (3401 Ashton Blvd) • Variety of PHP related topics • Mostly local speakers, occasional traveling speaker • Networking with other developers, companies • Professional development • uphpu.org

DATA TYPES IN PHP

OVERVIEW

DATA TYPES IN PHP

• Identify and define each type • Proper usage • Type juggling • Data type traps

• Defensive coding • Unit tests

CAN YOU NAME ALL THE DATA TYPES?

IDENTIFY AND DEFINE

DATA TYPES IN PHP

• 8 data types • 4 scalar • 2 compound • 2 special

IDENTIFY AND DEFINE

DATA TYPES IN PHP

• Scalar • string • integer • float (double) • boolean

• Compound • array • object

• Special • null • resource

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Scalar Compound Special

string array null

integer object resource

float

boolean

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Scalar Compound Special

‘Hello world’ [1, 2, 3] null

123 new X fopen

12.34

TRUE

STRING

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $var = ‘Hello world!’; • Series of characters • Up to 2GB • Scalar type • is_string

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $name = ‘Alice’; • Single quote: $var = ‘Hello $name’; • Output: Hello $name

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $name = ‘Alice’; • Double quote: $var = “Hello $name”; • Output: Hello Alice

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $name = ‘Alice’; • Heredoc: $var = <<<EOD

Hello $name EOD;

• Output: Hello Alice

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $name = ‘Alice’; • Nowdoc: $var = <<<‘EOD’

Hello $name EOD;

• Output: Hello $name

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $name = ‘Alice’; • $var = ‘Hello ‘ . $name; • $var = “Hello $name”; • $var = “Hello {$name}”; • $var = “Hello {$person[‘name’]}”; • $var = “Hello {$person->name}”; • Output: Hello Alice

IDENTIFY AND DEFINE

DATA TYPES IN PHP

String • $escaped = ‘\t’;

• Output: 't'

• $escaped = “\t”; • Output: ‘ ‘

IDENTIFY AND DEFINE

DATA TYPES IN PHP

INTEGER

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Integer • $number = 16; • Scalar type • Positive or negative: -16 or 16 • is_int or is_integer

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Integer • Decimal (base 10): 16 • Hexadecimal (base 16, leading 0x): 0x10 • Octal (base 8, leading 0): 020 • Binary (base 2, leading 0b): 0b10000

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Integer • Max 2,147,483,647 on 32-bit system • Max 9,223,372,036,854,775,807 on 64-bit system • Becomes a float if too big

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Integer • Automatically converted to float in math where result is not a

whole number • 16 / 2 = integer 8 • 16 / 3 = float 5.3333333333333 • (int) ((0.1 + 0.7) * 10) = (int) 7

• Precision with floats • Float to integer always rounded toward zero

FLOAT

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • $var = 12.34; • Scalar type • Double • Floating-point number • Real numbers • is_float, is_double, or is_real

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • Uses IEEE 754 standard for calculations

• Arithmetic formats • Interchange formats • Rounding rules • Operations • Exception handling (overflow, divide by zero)

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • $var = 12.34 • $var = 12.3e4 • $var = 12E-3

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • Precision varies by platform • Limited precision • Uses base 2 under the hood • Prone to accuracy problems

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • (0.1 + 0.7) * 10 = 7.9999… • floor((0.1 + 0.7) * 10) = 7

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • Use libraries for float math like BC Math or gmp

• bcadd, bcmul • gmp_add, gmp_mul

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • BCMath Arbitrary Precision Mathematics • bcxxx($leftOperand, $rightOperand [, $scale]) • bcscale($scale) • bcadd($a, $b) • bcmul($a, $b) • bcdiv($a, $b)

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • GNU Multiple Precision • gmp_xxx($leftOperand, $rightOperand [, $rounding])

• GMP_ROUND_ZERO • GMP_ROUND_PLUSINF • GMP_ROUND_MINUSINF

• gmp_init($number) • gmp_add($a, $b) • gmp_mul($a, $b) • gmp_div($a, $b, GMP_ROUND_ZERO)

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Float • Keep precision in mind • Use libraries for accuracy

BOOLEAN

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Boolean • $var = true; • Scalar type • Boolean or Bool • Only two possible values: true or false • is_bool

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Boolean • $var = true; • 0 == false • 1 == true • 2 == true • -1 == true • 3.45 == true • ‘abc’ == true • ‘false’ == true

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DATA TYPES IN PHP

Boolean • true === true • false === false

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DATA TYPES IN PHP

Boolean • Good to work with • Simplify checks

ARRAY

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • $var = [1, 2, 3]; • Compound type • is_array

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • $var = [1, 2, 3, 4.56]; • $var = [‘abc’, ‘xyz’]; • $var = [‘fruit’ => ‘apple’, ‘vegetable’ => ‘carrot’]; • $var = array(‘key’ => ‘value’); • $var[‘key’] = ‘value’; • $var[] = ‘value’; • $var{123} = ‘value’; • $var = explode(‘,’, $csv);

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • Ordered map • Keys and values

• Keys are integer or string • Value can be of any data type • If adding value to array then key = max numeric key + 1

where max numeric key is max that has existed since last re-index

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Data Type Key Key Cast As

string ‘abc123' ‘abc123'

string ‘123’ 123

float 12.34 12

bool true 1

null null ‘'

array […] Illegal offset

object new X Illegal offset

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • foreach ($array as $key => $value) { … } • foreach ($array as &$value) { … } • for ($i = 0; $i < count($array); $i++) { … }

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • Many useful array functions • ksort • asort • array_keys • array_key_exists

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Array • array_merge • array_intersect • array_column

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DATA TYPES IN PHP

Array • array_push • array_pop • array_shift • array_unshift • array_splice

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DATA TYPES IN PHP

Array • Use wisely • Use available array functions • Avoid overly nested arrays • Watch key casting

OBJECT

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • $var = new X; • Compound type • is_class • instanceof

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DATA TYPES IN PHP

Object • $var = new X; • $var = new X($value); • $var->doSomething($parameter); • $var::staticMethod(); • $var::SOME_CONSTANT;

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DATA TYPES IN PHP

Object • Constants • Properties • Methods • Magic methods • Visibility modifiers • Final keyword

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DATA TYPES IN PHP

Object class RainbowTrout extends Fish implements MarineLife { use Camouflage; const SPECIES = ‘Rainbow Trout’; protected $age; public function swim() { … } protected function breathe() { … } public function eat(Food $food) { … } private function ponder(Thought $thought) { … } }

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Abstract • Interface • Trait

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DATA TYPES IN PHP

Object • Abstract

• Vertical inheritance via extend • class Dog extends Canine • Is X a Y? • Code reusability • Ensure functionality • Only extend one class at a time • Can have multiple levels • Cannot be instantiated

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Abstract

• abstract Canine { public function wagTail() { … } abstract public function run(); }

• class Dog extends Canine { public function run() { … } }

• $dog = new Dog; $dog->wagTail(); $dog->run();

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Interface

• Class implements an interface • Define required method signatures • Does not define content of methods • Class defines the implementation • What class needs to do, not how to do it

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Interface

• interface PlayFetch { public function retrieveItem(Item $item); }

• class Dog implements PlayFetch { public function retrieveItem(Item $item) { … } }

• class Child extends Human implements PlayFetch, TakeNap { public function retrieveItem(Item $item) { … } public function fallAsleep() { … } }

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Trait

• Characteristic • Attribute • Reusable group functionality • Horizontal inheritance • Cannot be instantiated • Can use multiple traits • Vertical inheritance considerations • Dependency injection considerations

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Trait

• trait Hair { protected $color; public function setHairColor($color) { … } public function washHair($shampoo) { … } }

• class Cat extends Feline { use Hair; } • $cat = new Cat;

$cat->setHairColor(‘grey’); $cat->washHair($shampoo);

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Type hinting

• Method signatures • public function doSomething(X $x, array $y) { … }

• Doc blocks • /** @var integer */

• Method return type hint as of PHP 7 • public function sum($a, $b): integer { … }

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Object • Heavily used with PHP applications • Advanced functionality • Inheritance • Code reuse

NULL

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Null • $var; • $var = null; • Special type • Represents no value • is_null

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DATA TYPES IN PHP

Null • public function doNothing() {} • $value = $object->doNothing();

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DATA TYPES IN PHP

Null • $value = null; • Works: empty($value) === true • Best: is_null($value) === true

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DATA TYPES IN PHP

Null • unset($value) • $value becomes null

RESOURCE

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Resource • Special type • Reference to an external resource

• Database connection • Open files • Certificates • Image canvas

• get_resource_type • is_resource

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Resource • $resource = new mysqli(…); • $handle = fopen($fileName, ‘r’); • $privateKey = openssl_pkey_new([…]);

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Resource • Can be closed manually • Automatically closed when no more references • Memory freed by garbage collector • Exception to the rule are persistent database connections

IDENTIFY AND DEFINE

DATA TYPES IN PHP

Resource • Cannot cast to resource

DEFENSIVE CODING

DEFENSIVE CODING

DATA TYPES IN PHP

Defensive Coding • Hope for the best and prepare for the worst • Type hinting • Type checking • Type casting

DEFENSIVE CODING

DATA TYPES IN PHP

DEFENSIVE CODING

DATA TYPES IN PHP

Type Hinting • Use heavily • Provides documentation • Supports ‘Fail fast’ • Ensures data is of correct type or instance • Makes code easier to read and understand by peers

DEFENSIVE CODING

DATA TYPES IN PHP

Type Hinting • Method parameters

• protected function doSomething(int $a, float $b, bool $c, array $d, X $x) { … }

• Method return • private function doOther(SomeClass $someClass): someClass

{ … }

DEFENSIVE CODING

DATA TYPES IN PHP

Type Checking • Use proper data type checks

• is_null instead of empty • is_float instead of is_numeric • === when possible • instanceof checks • count vs empty

DEFENSIVE CODING

DATA TYPES IN PHP

Comparison Operators Loose Strict

Operator == ===

Type Check No Yes

Type Conversion Yes No

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Automatic • Manual

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Automatic

• PHP is a loosely typed language • Variable data type can change • Particularly with going to string or integer • Unintentionally introduce defects • ‘1’ + ‘2’ === 3 • 1 + ‘1 way’ === 2

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (int) false === 0 • (int) 12.34 === 12 • (int) ‘123abc’ === 123

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (string) false === ‘’ • (string) true === ‘1’ • (string) 12.34 === ’12.34’

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (bool) ‘false’ === true • (boolean) 1 === true

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (float) ’12.34’ === 12.34 • (double) 12 === 12 • (real) ‘’ === 0

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (array) ‘scalar’ === [‘scalar’] • (array) new Exception === [‘* message’ => ‘’, ‘Exception

string’ => ‘’, ‘* code’ => 0, ‘* file’ => ‘/path/to/file.php’, ‘* line’ => 123, ‘Exception trace’ => […], ‘Exception previous’ => null] • Classname key for private • Asterisk * for protected

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (object) [1, 2, 3] becomes stdClass{public 0 = 1; public 1 = 2;

public 3 = 2;} • (object) ‘something’ becomes stdClass{public ‘scalar’ =

‘something’;} • (object) null becomes stdClass{}

DEFENSIVE CODING

DATA TYPES IN PHP

Type Casting • Manual

• Cast variable as a specific type • (unset) ‘anything’ === null • (unset) $value === null

• returns null • $value retains existing value

UNIT TESTS

UNIT TESTS

DATA TYPES IN PHP

Unit Tests • Automated way to test code • Data type checks • Value checks • Code behaves as expected

UNIT TESTS

DATA TYPES IN PHP

Setup • Via composer

• Add to composer.json: • “require-dev”: {“phpunit/phpunit”: “5.4.*”}

• composer update • Via download

• wget https://phar.phpunit.de/phpunit.phar chmod +x phpunit.phar sudo mv phpunit.phar /usr/local/bin/phpunit

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • Create /tests/ directory • Files named *Test.php • If using composer

• require_once __DIR__ . ‘/../vendor/autoload.php’; • use PHPUnit\Framework\TestCase;

class FilenameTest extends TestCase { … }

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • Focus today is on data types • Data providers to provide test data sets

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertEquals($expected, $actual [, $message])

• Value is equal • No data type check • ==

• assertSame($expected, $actual [, $message]) • Value is equal • Data type is same • ===

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • Use setUp to set class

• protected function setUp() { parent::setup(); $this->intMath = new IntMath; }

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • Use data providers to use test data sets • /** @dataprovider intAdditionProvider */

public function testAddInts($a, $b, $expected) { $this->assertSame($expected, $this->IntMath->add($a, $b)); } public function intAdditionProvider() { return [ [0, 0, 0], [1, 2, 3], [-1, 1, 0] ]; }

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertContains($needle, $haystack [, $message, $ignoreCase])

• Value (needle) exists in haystack • Defaults to not ignore case

• assertContainsOnly($type, $haystack [, $isNativeType, $message]) • Is type the only data type in the haystack

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertFalse($condition [, $message]) • assertNotFalse($condition [, $message]) • assertTrue($condition [, $message]) • assertNotTrue($condition [, $message])

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertNull($variable [, $message]) • assertNotNull($variable [, $message])

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertInstanceOf($expected, $actual [, $message]) • assertContainsOnlyInstancesOf($classname, $haystack [,

$message]) • Instance checks in array or Traversable

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertLessThan • assertLessThanOrEqual • assertGreaterThan • assertGreaterThanOrEqual

UNIT TESTS

DATA TYPES IN PHP

Create Class With Tests • assertRegExp($pattern, $string [, $message]) • assertNotRegExp

SUMMARY

DATA TYPES IN PHP

SUMMARY

• 8 data types • string • integer • float • boolean • array • object • null • resource

DATA TYPES IN PHP

SUMMARY

• Use data types correctly • Code defensively • Be aware of automatic type casting • Prefer strict type checks • Unit tests to ensure correct values

QUESTIONS?https://joind.in/talk/6d7f9

SOURCES

DATA TYPES IN PHP

• php.net • https://phpunit.de/manual/current/en/ • https://getcomposer.org/doc/00-intro.md