if

has only one section:

Condition

if (Condition) {
    // Code to be executed
}

for

loop has three sections divided by

;

for (Initialization;   Condition;   Increment/Decrement) {
    // Code to be executed
}

The loop prints numbers from 0 to 10

for ($i = 0;  $i < 10;  $i ++) {
	echo $i . "\n";
}

Function that does something

function printGreeting() {
	print "Prints: Hello world!\n";
}
printGreeting();

Function that returns something

function returnGreeting() {
	return "Returns: Hello world!\n";
}
echo returnGreeting();

Parameterized function that doubles the number

function doubleMe($number) {
	$result = "$number times 2 is: " . $number * 2 . "\n";
	return $result;
}
echo doubleMe(4);

Function calculates the sum of two numbers

function add($num1, $num2) {
	$sum = $num1 + $num2;
	$result = "Sum of $num1 and $num2 is: $sum";
	return $result;
}
echo add(4, 5);

The code will output "Have a nice weekend!" if the current day is Friday, and "Have a nice Sunday!" if the current day is Sunday, otherwise it will output "Have a nice day!"

$d = date("D");
if($d == "Fri"){
    echo "Have a nice weekend!";
} elseif($d == "Sun"){
    echo "Have a nice Sunday!";
} else{
    echo "Have a nice day!";
}
echo "\n";

Outputs

Have a good morning!

if the current time is less than 10, and

Have a good day!

if the current time is less than 20. Otherwise it will output

Have a good night!

$t = date("H");
if ($t < "10") {
	echo "Have a good morning!";
} elseif ($t < "20") {
	echo "Have a good day!";
} else {
	echo "Have a good night!";
}

Prints

Adult

If

$age

is more than

18

, and

Teenager

if the variable is less than 12. Otherwise it prints

Child

$age = 20;
if ($age > 18) {
    echo 'Adult';
} else if ($age > 12) {
    echo 'Teenager';
} else {
    echo 'Child';
}

The code will output "Have a nice weekend!" if the current day is Friday, otherwise - "Have a nice day!"

$d = date("D");
if($d == "Fri"){
    echo "Have a nice weekend!";
} else{
    echo "Have a nice day!";
}
echo "\n";

Output "Have a good day!" if the current time is less than 20, and "Have a good night!" otherwise:

$t = date("H");
if ($t < "20") {
    echo "Have a good day!";
} else {
    echo "Have a good night!";
}

If

$age

is more than

18

, prints

Adult

otherwise prints

Child

$age = 20;
if ($age > 18) {
    echo 'Adult';	
} else {
    echo 'Child';	
}

If the current day is Friday the code will output "Have a nice weekend!" PHP datetime format: https://www.php.net/manual/en/datetime.format.php

$d = date("D");
if ($d == "Fri"){
    echo "Have a nice weekend!";
}

If the current hour is less than 20, the code will output "Have a good day!"

$t = date("H");
if ($t < "20") {
  echo "Have a good day!";
}

If

$age

is more than

18

, prints

Adult

$age = 20;
if ($age > 18) {
	echo 'Adult';	
}

Indexed array

$colors = ["Red", "Green", "Blue"];
$colors[] = "Yellow";

Associative arrays

$student = [
	"name"=>"George", 
	"weight"=>77, 
	"height"=>1.8, 
	"male"=>true
];
$student["male"] = true;
echo 'George is ' . $student['weight'] . 'kg'."\n";

Multidimensional arrays

$students = [
	"George"=> [
		"name"=>"George", 
		"weight"=>77, 
		"height"=>1.8, 
		"male"=>true
	],
	"Alex"=> [
		"name"=>"Alex", 
		"weight"=>87, 
		"height"=>2.8, 
		"male"=>true,
		"parents"=> [
			"father"=>"David",
			"mother"=>"Marta",
		]
	],
	
];
echo 'Alex weighs ' . $students['Alex']['weight'] . 'kg'."\n";
echo "Alex's father is: " . $students['Alex']['parents']['father'];

Function

min()

finds the lowest value from its arguments

echo min(10, 15, 7, 9, 17)."\n"; // 7

Function

max()

finds the highest value from its arguments

echo max(10, 15, 7, 9, 17)."\n"; // 17

Function

count()

counts all elements in the array

echo count([10, 15, 7, 9, 17])."\n";

Function

round()

rounds a floating-point number to its nearest integer

echo(round(0.75))."\n";  // returns 1
echo(round(0.5))."\n";  // returns 1
echo(round(0.49))."\n";  // returns 0

Function

floor()

rounds the floating-point number down

echo floor(3.3)."\n";// 3  
echo floor(7.84)."\n";// 7 
echo floor(-4.8)."\n";// -5  

Function

ceil()

rounds the floating-point number up

echo ceil(3.3)."\n";// 4
echo ceil(7.84)."\n";// 8
echo ceil(-4.8)."\n";// -4

Function

rand()

generates a random number

echo rand()."\n";
// Generates a random number from the range
echo rand(10, 100)."\n";

Function

sqrt()

returns the square root of a number

echo sqrt(64)."\n";  // 8

Function

pow()

raises 2 to the power of 3

echo pow(2, 3)."\n";  // 8

Function

pi()

Returns PI value

echo pi()."\n";// 3.1415926535898

Function

abs()

returns the positive (absolute) value of a number

echo abs(-12)."\n";

Function

decbin()

converts decimal number into binary

echo decbin(2)."\n";// 10 

Function

strlen()

returns the length of the string

echo strlen("Hello world!")."\n"; // 12

Function

strrev()

returns the Reverse of the string

echo strrev("Hello world!")."\n"; // !dlrow olleH

Function

strpos()

tries to find the second parameter and returns its index

echo strpos("Hello world!", "world")."\n"; // 6

Function

str_replace()

replaces the word "Hello" with "Hi"

echo str_replace("Hello", "Hi", "Hello there")."\n"; // Hi there

Function

substr()

returns the substring between given indexes

echo substr("Hello world", 6)."\n"; // world
echo substr("Hello world", 6, 3)."\n"; // wor
echo substr("Hello world", -5)."\n"; // world
echo substr("Hello world", -4, 2)."\n"; // or

Function

trim()

removes whitespaces from sides of the string

echo trim("   Hello World  ").".\n"; // Hello World.
// Removes whitespaces from the right end
echo rtrim("   Hello World  ")."\n"; //    Hello World
// Removes Exclamation mark from the right end
echo rtrim("Hello World!", "!")."\n"; // Hello World

Function

strtoupper()

converts the string to upper case

echo strtoupper("Hello World")."\n";

Function

strtolower()

converts the string to lower case

echo strtolower("Hello World")."\n";

Function

explode()

breaks the string by its delimiter

print_r (explode(" ", "It's the first day of the course!"));

Function

implode()

joins the array element based on the delimiter and returns the string

echo implode(" ", ['Hello', 'World']);

The three variables

$variable

,

$Variable

and

$VARIABLE

are completely different

// lowercase
$variable = "Value 1";

// PascalCase
$Variable = "Value 2";

// UPPERCASE
$VARIABLE = "Value 3";

echo $variable . "\n";
echo $Variable . "\n";
echo $VARIABLE . "\n";

Function names are case-insensitive

function printGreeting() {
	print "Prints: Hello world!\n";
}
printGreeting();

Calling the function with uppercase will still work

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