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Defining namespace :

Any valid PHP code can be contained within a namespace. But only the folowing types of code are affected by namespaces :

classes (including traits and abstracts)
functions
constantes

A file containg a namespace keyword must declare the namespace at the top of file and before any code. The only code allowed before namespace declaration is the declare statement for defining the encoding.

Post increment vs pre increment

<?php
$i = 10;
$a = $i++;
// Now $a is 10, and $i is 11

$i = 10;
$a = ++$i;

GLOBALS :

An associative array containg references to all variables defined in the global scope of the script. The variable names are the keys of the array

$_SERVER :

Is an array that containing inforamtion such as headers, paths and script locations.

Prior to PHP 5.4.0, $HTTP_SERVER_VARS contained the same initial information, but was not a superglobal. (Note that $HTTP_SERVER_VARS and $_SERVER were different variables and that PHP handled them as such.)

⛔ You may or may not find any of the following elements in $_SERVER if running PHP on the command line.

Error handling

Predefined constants :

Default errors :

Value	Constant	Description
1	E_ERROR	Fatal run-time errors. Execution of the script is halt.
2	E_WARNING	Run-time warnings. Execution of the the script is not halted.
4	E_PARSE	Compile-time errors. Should only be generated by the parser.

🚫 Functions names are case-insensitive !

<?php

define('CONSTANT', 1);
define('_CONSTANT', 0);
define('EMPTY', '');

if (!empty(EMPTY)) {

Installation :

This extensio is enabled by default. It may be disabled by using the following option at compile time : --disable-xml if you comiple PHP ad a module for Apache
This extension has no configuration directives defined in php.ini

XML Parser functions :

xml_parser_create -> create an XML parser. xml_parser_create_ns -> create an XML parser with namespace support.

Character encoding :

The XML DOM Parser :

The DOM parser is a tree-based parser.

Load and Output XML :

Exp :

<!-- file.xml -->
<?xml version="1.0" encoding="UTF-8"?>
<note>
    <to>Tove</to>

SAOP and PHP

SAOP is an acronym for Simple Object Access Protocol. It is an XML-based messaging protocol for exchanging information. SAOP is an application of the XML specification.

Points to note :

SOAP is a communication protocol designed to communicate via internet.
SAOP provides data transport for Web Services.
SOAP is a platform and language-independent.
SOAP is the XML way of defining what information is sent and how.

JSON and PHP

Json is an acronym for JavaScript Object Notation
DATA-interchange format
🔥 extension load in PHP by default

PREDEFINED CONSTANTS (examples)

JSON_ERROR_NONE confirms whether error occurred or not
JSON_ERROR_SYNTAX indicates syntax error
JSON_ERROR_UTF8 encoding issues

	<?php
	namespace bar;
	class Xyz
	{
	}
	function abc()
	{
	return __NAMESPACE__;