CSS3 introduced these notations (with two colons) to distinguish pseudo-classes from pseudo-elements. Browsers also accept

:after

,

:before

,

:first-letter

,

:first-line

, introduced in CSS2

Installs the latest version of the package

npm install package  /  npm install package@latest

Different types of Variables

$name = "George";
$age = 25;
$weight = 75; //kg
$height = 1.85; //m

Variables used in expressions

echo "His name is ".$name."\n";
echo "He is ".$age." years old\n";
echo "He weighs around ".$weight."\n";
echo "he is ".$height."m tall \n";

String

$name = "George";

Integer

$weight = 85; //kg

Float

$height = 1.9; //m

Boolean

$male = true;

Array

$colors = ["Red", "Green", "Blue"];
// Instead of storing them in separate variables like this:
$color1 = "Red";
$color2 = "Green";
$color3 = "Blue";

gettype()

returns a type of a given variable

echo gettype($my_name); // string

- A variable starts with the

$

sign, followed by the name of the variable - A variable name must start with a letter or the underscore character - A variable name cannot start with a

number

- A variable name can only contain alpha-numeric characters and underscores (

A-z

,

0-9

, and

_

)

// Correct Syntax
$variable_name = "Value";

// Incorrect Syntax
Variable_Name = "Value";
$5variable_name = "Value";
$variable-name = "Value";

Sets

timezone

using

php.ini

file

date.timezone = Asia/Tbilisi

Sets

timezone

inside php script file

ini_set('date.timezone', 'Asia/Tbilisi');

Arithmetic operators work with:

integer

and

float

values to perform arithmetical operations. Let's define two variables:

number1

and

number2

and perform these operations

$number1 = 40;
$number2 = 9;

Addition

echo $number1 + $number2 . "\n";

Subtraction

echo $number1 - $number2 . "\n";

Multiplication

echo $number1 * $number2 . "\n";

Division

echo $number1 / $number2 . "\n";

Modulus

echo $number1 % $number2 . "\n";

Prints plain text

echo 'plain text'."\n";

Double quotes can parse variables

echo "Double quotes: $text"."\n";

Single quotes can not parse variables

echo 'Single quotes: $text'."\n";

Single quotes as well as double quotes can be concatenated with variables

echo 'Single quotes - '.$text." - Double quotes"."\n";

Text inside Single quotes can include double quotes as part of the text

echo 'The text includes "double" quotes as part of the text'."\n";

Text inside double quotes can include single quotes as part of the text

echo "Jane's surname is Smith"."\n";

echo can be used as a function

echo ('echo as a function')."\n";

echo can print number without quotes

echo 5 . $number;

echo

can take multiple parameters

echo 'one', 'two', 'three', "\n";

We can print multiple lines of text

echo 'Prints text 
    with multiple
lines';

Single line comment

// $variable = 'Value';

Another single line comment

# $variable = 'Value';

Comment for multiple lines

/*$variable = 'Value';
$second_variable = 'Value 2';
$third_variable = 'Value 3';*/

Inline comment

$number = 5 /* - 5  */ + 5;

Prints the text

Hello world

echo "Hello world";

Prints the two words one by one

echo "Hello ";
echo "world";

Prints the variable

$greeting

$greeting = "Hello world";
Echo $greeting;

Concatenates the string to the variable

$greeting

$greeting = "hello world!";
Echo $greeting . " Let's get started!";