Eric The Coder

Posted on Dec 17, 2020 • Updated on Sep 9, 2021

My beloved PHP cheat sheet

#php #laravel #beginners

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 'red':
        echo 'The color is red';
        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);

// 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) {
    ...
}

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;
    }
}

//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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Latest comments (13)

Constantin Coșoiu • Sep 11 '23

Very very useful and concise. Do you have it as a 1 or 2 pages PDF?

Chris Brown • Dec 20 '20 • Edited

Nice list. Note: In at least 2 cases you use __construc where it should be __construct

Eric The Coder • Dec 20 '20

Good catch. Corrected.

Ellis • Dec 20 '20

I need to benchmark it again, but ++$i is a micro optimizion you can use on your for loops. IIRC, do..while is another micro optimization you replace your while loops with, if you can guarantee at least one iteration.

Jon Randy 🎖️ • Dec 19 '20

<?php

//Naming convention
$first_name = 'Mike'. // all lower case with underscore separators
function updateProduct() // camelCase
class ProductItem // StudlyCaps
const ACCESS_KEY = '123abc'; // all upper case with underscore separators

//output
echo 'Hello World';

//variable declaration
$name = 'Mike'; //string
$isActive = true; //boolean
$number = 25; //integer
$amount = 99.95; //float
...