<?php
 
function mb_ucfirst(string $str, ?string $encoding = null): string
{
    return mb_convert_case(
    	mb_substr($str, 0, 1, $encoding), 
        MB_CASE_TITLE, 
        $encoding
    ) 
    	. mb_substr($str, 1, null, $encoding)
    ;
}

function mb_lcfirst(string $str, ?string $encoding = null): string
{
    return mb_strtolower(
    	mb_substr($str, 0, 1, $encoding), 
        	$encoding
        ) 
    	. mb_substr($str, 1, null, $encoding)
    ;
}

<?php


function get_contents() {
  file_get_contents("http://example.com");
  
  // Variable secretly created in the local scope
  // Array of headers as strings
  var_dump($http_response_header); 
}
get_contents();

// Warning: Undefined varable $http_response_header
var_dump($http_response_header); 

<?php

array(9) {
  [0]=>
  string(15) "HTTP/1.1 200 OK"
  [1]=>
  string(35) "Date: Sat, 12 Apr 2008 17:30:38 GMT"
  [2]=>
  string(29) "Server: Apache/2.2.3 (CentOS)"
  [3]=>
  string(44) "Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT"
  [4]=>
  string(27) "ETag: "280100-1b6-80bfd280""
  [5]=>
  string(20) "Accept-Ranges: bytes"
  [6]=>
  string(19) "Content-Length: 438"
  [7]=>
  string(17) "Connection: close"
  [8]=>
  string(38) "Content-Type: text/html; charset=UTF-8"
}

# <=8.3
  opcache.jit=tracing
  opcache.jit_buffer_size=0
  
# >= 8.4
  opcache.jit=disable
  opcache.jit_buffer_size=64m

<?php
 
function foo(T1 $a, T2 $b = null, T3 $c) {}

function bar(T1 $a, ?T2 $b = null, T3 $c) {}

function test(T1 $a, T2|null $b = null, T3 $c) {}

<?php
 
// Only support <=HTML4.01
\DOMDocument::loadHTML()
\DOMDocument::loadHTMLFile()

// Supports HTML5
\DOM\HTMLDocument::createEmpty()
\DOM\HTMLDocument::createFromFile()
\DOM\HTMLDocument::createFromString()

// Drop in replacement for \DOMDocument
\DOM\XMLDocument::createEmpty()
\DOM\XMLDocument::createFromFile()
\DOM\XMLDocument::createFromString()

<?php
 
// This is a PUT request
var_dump($_POST);  // []
var_dump($_FILES); // []
 
[$_POST, $_FILES] = request_parse_body();
 
var_dump($_POST);  // [...]
var_dump($_FILES); // [...]

<?php
 
ceil($number) === round($number, 0, PHP_ROUND_CEILING); //true
floor($number) === round($number, 0, PHP_ROUND_FLOOR); //true