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Here is my cheat sheet I created along my learning journey. If you have any recommendations (addition/subtraction) let me know.
PHP local server
php -S localhost:3000
Comments
// one line comment
/*
This is a multiple-lines comment block
that spans over multiple
lines
*/
Naming conventions
// PHP opening/closing tag
<?php
echo "Hello World";
?>
// if no closing tag the rest of the file will be considered PHP
// Short syntax for PHP echo
<?= "Hello World" ?>
//Enable strict typing (first line of your PHP file)
<? declare(strict_types=1);
// Include a PHP file
require 'app/Product.php'
// Create a namespace
namespace App;
// Use a namespace
use App\Product;
$firstName = 'Mike' // camelCase
function updateProduct() // camelCase
class ProductItem // StudlyCaps
const ACCESS_KEY = '123abc'; // all upper case with underscore separators
Output & Input
echo 'Hello World';
// Debug output
var_dump($names);
print_r($products);
// Input from console
$name = readline('What is your name : ');
Variables Declaration
$name = 'Mike'; //string
$isActive = true; //boolean
$number = 25; //integer
$amount = 99.95; //float
$fruits = ['orange', 'apple', 'banana'] //array
const MAX_USERS = 50; //constant
define('MAX_USERS', 50); //constant
// Assign 'by reference' with the & keyword
$name_2 = &$name_1
// Type conversion
$age = (int)readline('Your age: ');
echo 'Your age is' . (string)$age;
echo gettype($age); // int
echo is_int($age) // true
echo is_float(12.5) // true
echo is_string($name) // true
Strings
// String can use single quote
$name = 'Mike'
// or double quote
$name = "Mike"
// Double quote string can escape characters \n = new line \t = tab \\ = backslash
echo "Hello Mike\nHello David";
// Double quote string can do interpolation
echo "Hello $name";
// string concat
echo 'Hello ' . $name;
// string length
echo strlen($name);
// Remove space(s) before and after
echo trim($text)
// Convert to lowercase / uppercase
echo strtolower($email);
echo strtoupper($name);
// Converts the first character to uppercase
echo ucfirst($name); // 'Mike'
// Replace text a by text b in $text
echo str_replace('a', 'b', $text);
// String Contains (PHP 8)
echo str_contains($name, 'ke') # true
// Find numeric position of first occurrence
$pos = strpos($name, 'k'); # 2
// Returns portion of string (offset / length)
echo substr($name, 0, $pos); # Mi
Numbers
// Shortcut addition assignment
$value = 10
$value++ // 11
// or
$value += 1 // 11
// Shortcut subtraction assignment
$value = 10
$value-- // 9
// or
$value -= 1 // 9
// Check if numeric
echo is_numeric('59.99'); # true
// Round a number
echo round(0.80); // returns 1
// Round a number with precision
echo round(1.49356, 2)); // returns 1.49
// Random number
echo(rand(10, 100)); # 89
Conditionals
// If / elseif / else
if ($condition == 10) {
echo 'condition 10'
} elseif ($condition == 5) {
echo 'condition 5'
} else {
echo 'all other conditions'
}
// And condition = &&
if ($condition === 10 && $condition2 === 5) {
echo '10 and 5'
}
// Or condition = ||
if ($condition === 10 || $condition2 === 5) {
echo '10 or 5'
}
// One line
if ($isActive) return true;
// Null check
if (is_null($name)) {
do something...
}
//Comparaison operation
== // equal no type check
=== // equal with type check
!= //not equal
|| //or
&& //and
> //greater than
< //less than
// Ternary operator (true : false)
echo $isValid ? 'user valid' : 'user not valid';
//Null Coalesce Operator
echo $name ?? 'Mike'; //output 'Mike' if $name is null
//Null Coalesce Assignment
$name ??= 'Mike';
// Null Safe Operator (PHP 8) will return null if one ? is null
echo $user?->profile?->activate();
// Null Safe + Null Coalesce (if null will return 'No user profile')
echo $user?->profile?->activate() ?? 'Not applicable';
//Spaceship operator return -1 0 1
$names = ['Mike', 'Paul', 'John']
usort($names, function($a, $b) {
return $a <=> $b;
}
// ['John', 'Mike', 'Paul']
// Return false when convert as boolean
false, 0, 0.0, null, unset, '0', '', []
// Compare same variable with multiple values
switch ($color) {
case 'red':
echo 'The color is red';
break;
case 'yellow':
echo 'The color is yellow';
break;
case 'blue':
echo 'The color is blue';
break;
default:
echo 'The color is unknown';
}
// Match Expression (PHP 8)
$type = match($color) {
'red' => 'danger',
'yellow', 'orange' => 'warning',
'green' => 'success',
default => 'Unknown'
};
// Check if variable declare
isset($color['red']); # true
Loops and Iterations
//for loop
for ($i = 0; $i < 20; $i++) {
echo "i value = " . i;
}
//while loop
$number = 1;
while ($number < 10) {
echo 'value : ' . $number ;
$number += 1;
}
//do while
$number = 1;
do {
echo 'value : ' . $number ;
$number += 1;
} while ($number < 10);
// foreach with break / continue exemple
$values = ['one', 'two', 'three'];
foreach ($values as $value) {
if ($value === 'two') {
break; // exit loop
} elseif ($value === 'three') {
continue; // next loop iteration
}
}
Arrays
//Array declaration can contain any types
$example = ['Mike', 50.2, true, ['10', '20']];
//Array declaration
$names = ['Mike', 'Peter', 'Shawn', 'John'];
// Direct access to a specific element
$name[1] //output Peter
// How to access an array in an array
$example[3][1] // 20
//add a element to an array
$names[] = 'Micheal';
// Array merge
$array3 = array_merge($array1, $array2);
// Merge with spreading operator (also work with associative array)
$array3 = [...$array1, ...$array2];
// Array Concat with Spread Operator
$names = ['Mike', 'Peter', 'Paul'];
$people = ['John', ...$names]; // ['John', 'Mike', 'Peter', 'Paul']
//Remove array entry:
unset($names['Peter']);
//Array to string
echo implode(', ', $names) //output Mike, Shawn, John, Micheal
// String to Array
echo explode(',', $text); // ['Mike', 'Shawn', 'John']
//loop for each array entry
foreach($names as $name) {
echo 'Hello ' . $name;
}
// Number of items in a Array
echo count($names);
//Associative array declaration (key => value):
$person = ['age' => 45, 'genre' => 'men'];
//Add to ass. array:
$person['name'] = 'Mike';
//loop ass. array key => value:
foreach($names as $key => $value) {
echo $key . ' : ' . $value
}
// Check if a specific key exist
echo array_key_exists('age', $person);
// Return keys
echo array_keys($person); // ['age', 'genre']
// Return values
echo array_values($person) // [45, 'men']
//Array filter (return a filtered array)
$filteredPeople = array_filter($people, function ($person) {
return $names->active;
})
// Array map (return transform array):
$onlyNames = array_map(function($person) {
return ['name' => $person->name];
}, $people)
# Search associative array
$items = [
['id' => '100', 'name' => 'product 1'],
['id' => '200', 'name' => 'product 2'],
['id' => '300', 'name' => 'product 3'],
['id' => '400', 'name' => 'product 4'],
];
# search all value in the 'name' column
$found_key = array_search('product 3', array_column($items, 'name'));
# return 2
Functions
//function declararion
function name($firstName, $lastName = 'defaultvalue') {
return "$firstName $lastName"
}
//function call
name('Mike', 'Taylor');
//function call with named parameters (PHP 8)
name(firstName: 'Mike', lastName: 'Taylor'); // order can change
//function variables params
function name(...$params) {
return $params[0] . “ “ . params[1];
}
// Closure function
Route::get('/', function () {
return view('welcome');
});
// Arrow functions
Route::get('/', fn () => view('welcome');
// Typed parameter and typed return
function display(string $first, string $last) : string {
return "$first $last";
}
// Typed or null
function display(?string $name) {
...
}
// Union type (or)
function display(string|int $data) {
...
}
// Intersection type (and)
function count_and_interate(Iterator&Countable $value) {
...
}
// Return any type (mixed)
function logInfo(string $info) : mixed {
...
}
// No return (void)
function logInfo(string $info) : void {
...
}
Enumerations
// Declaration
enum InvoiceStatus
{
case Sent;
case Paid;
case Cancelled;
}
// The enum can then be use as a type
function printInvoiceStatus(InvoiceStatus $status)
{
print($status->name);
}
printInvoiceStatus(InvoiceStatus::Sent);
// Sent
// enum with return value and public function exemple
enum InvoiceStatus : int
{
case Sent = 0;
case Paid = 1;
case Cancelled = 2;
public function text() : string
{
return match ($this) {
self::Sent => 'Sent',
self::Paid => 'Paid',
self::Cancelled => 'Cancelled'
};
}
}
function getInvoiceStatus(InvoiceStatus $status)
{
print($status->text());
print($status->value);
}
getInvoiceStatus(InvoiceStatus::Paid);
// Paid1
Files
// Get the current dir
$current_dir = __DIR__;
// Check if file exist
if (file_exists('/posts/first.txt')) {
do some stuff
}
// Read file content into one variable
$post = file_get_contents($file);
//File read
$file = fopen("test.txt", "r");
//Output lines until EOF is reached
while(! feof($file)) {
$line = fgets($file);
echo $line. "<br>";
}
fclose($file);
// File write
$file = fopen('export.csv', 'a');
$array = ['name' => 'Mike', 'age' => 45];
//Write key name as csv header
fputcsv($file, array_keys($array[0]));
//Write lines (format as csv)
foreach ($array as $row) {
fputcsv($file, $row);
}
fclose($file);
Errors
//Throw Error
if (someCondition) {
throw new Exception('Data format error');
}
//Catch the Error
try {
$db->checkData($data);
} catch (Exception $e) {
echo $e->getMessage();
}
OOP
//class declaration
class Person
{
}
// object instantiation
$person = new Person
//class properties and constructor
class Person
{
protected $firstName;
protected $lastName;
public function __construct($firstName, $lastName) {
$this->firstName = $firstName;
$this->lastName = $lastName
}
// Constructor Property Promotion (PHP 8)
class Person
{
public function __construct(protected $firstName, protected $lastName)
{
}
// Getter and Setter
class Person
{
private $name;
public function setName($name){
if(!is_string($name)){
throw new Exception('$name must be a string!');
}
$this->name = $name;
}
public function getName(){
return $this->name;
}
}
// Readonly properties (PHP 8.1)
class Person
{
public function __construct(
public readonly string $firstName,
public readonly string $lastName
) {
}
}
//static constructor
public static function create(...$params) {
return new self($params)
}
$person = Person::create(‘Mike’, ‘Taylor’);
// Static Method
class greeting {
public static function welcome() {
echo "Hello World!";
}
}
// Call static method
greeting::welcome();
// Static method call
class greeting {
public static function welcome() {
echo "Hello World!";
}
public function __construct() {
static::welcome();
}
}
new greeting();
// Static constant
class Connection
{
const MAX_USER = 100;
}
echo Connection::MAX_USER # 100
// class inheritance
class Customer extends Person
{
public function name()
{
parent::name();
echo 'Override method';
}
}
// self keyword reference current class (not modify by inheritance late binding like static will be)
self::welcome();
// Interface
interface Animal {
public function makeSound();
}
class Cat implements Animal {
public function makeSound() {
echo "Meow";
}
}
$animal = new Cat();
$animal->makeSound();
//Trait (mix-in)
trait HelloWorld {
public function sayHello() {
echo 'Hello World!';
}
}
class Greetings {
use HelloWorld;
}
$object = new Greetings();
$object->sayHello();
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