PHP Cheat Sheet

<?php
print('Hello, World!');

This code outputs "Hello, World!" to the browser. The print statement is used to display text or variables.

<?php print('Header'); ?>
Before <?php print('Hello, World!'); ?> after ...

Code outside the <?php ... ?> blocks is written to the output. You can use this to interleave HTML and PHP blocks.

<?php
$age = 42;
$message = "Your age is $age";
$fullMessage = "Welcome\n" . $message;
print($fullMessage);

You must use dollar sign '$' when using variables. There is no variable declaration. You concat strings using dot '.'.

<?php
print(htmlspecialchars('<hr>'));

Use htmlspecialchars to escape potentially dangerous content before outputting to HTML.

<?php
if ($name === "Ailish) { ... } else { ... }

Use === for equality test! Do not use == unless you know what you are doing. When using == add a comment with an explanation.

<?php
$people = ['Ailish', 'John'];

// Add a new item
$people[] = 'Paul';

// Iterate over items
foreach ($people as $index => $name) { ... }

Basic array syntax.

<?php
$student = ['name' => 'Ailish', 'age' => 22];

Using an array as a Python dictionary.

<?php
$jsonAsString = '{"name": "Ailish"}';

// Decode string
$data = json_decode($jsonAsString, true);

// Print the string representation
print($data);

// Encode back to a string
$json = json_encode(
  $data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES);

The second argument in json_decode is true when the returned object should be an associative array.

You can customize format of the output of json_encode function using flags.

<?php
// Read from a file next to the current script.
$content = file_get_contents(__DIR__ . '/data.json');

// Write to a file next to the current script.
file_put_contents(__DIR__ . '/data.json', $content);

You can read content using file_get_contents method. It can be used to read local and remote file as well. For a local file use __DIR__ to keep the path relative to current file.

The file_put_contents creates a file if it does not exists. You can use the flags to append to a file.

<?php
// Get data from URL query part.
var_dump($_GET);

// Get post data.
var_dump($_POST);

// Get request method.
var_dump($_SERVER['REQUEST_METHOD']);

Reading HTTP request's data.