references/php.md at reference · nitishsaini706/references

what is php ?

it stands for php:hypertext processor
it's files has .php extension
php files contain text , html , css , js and php code

basic syntax

php scripts starts with

<?php
	//code
?>

it normally contains html tags and php code
php statements ends with ;
it is not case sensitie , variables are case sensitive
we user // , # , /* */ for comments
it also has strict mode to enable it

<?php declare (strict_types=1);

?>

variables

$ sign is used , echo is used to display on screen

<?php

 $text = "hello";
echo " i m $text ";
// or 
echo "i m " . $text . " hello" ;
?>

variable scope = local , global , static
- we cannot use global variables inside function , we need to use global keywrod
- usually when function is executed all functino variables are deleted , to reuse them we use static keyword while declaring them

data types

string - first character is 0
int
float
bool
array
object
NULL
resource
we need to declare class object using class keyword

<?php

class car {
	function car( ){
		$this -> model="honde";
		     }
	}
// creating new object
$maruti = new car ( );
echo $maruti -> model;

?>

string functions

strlen( ) - used to get length of string , strlen("string");
str_word_count( ) - used to count words in string , str_word_count("string") ;
strrev( ) - reverse the string
strpos( ) - search text within string , strpos("hello world", "world");
str_replace ( "to replace ", "replace with" , "string" )

$name = "Harry is a good boy";
echo $name;
echo "<br>";

echo "The length of " . "my string is " . strlen($name);
echo "<br>";
echo str_word_count($name);
echo "<br>";
echo strrev($name);
echo "<br>";
echo strpos($name, "Harry");
echo "<br>";
echo str_replace("Harry", "Rohan", $name);
echo "<br>";
echo str_repeat($name, 4);
echo "<br>";
echo "<pre>";
echo rtrim("    this is a good boy     ");
echo "<br>";
echo ltrim("    this is a good boy     ");
echo "</pre>";

numbers

Nan - not a number
change variable type or type cast (type)$a
to create constant we use define ( ) function

define (name , value , case-insensitive (false by default) );

operators same as js
conditions

<?php

if (condition) 
{
	code ;
}
else if (condition) 
{
	code ; 
}
else
{ 
	code ;
}

switch(n) 
{	
	case label 1 :
		code ;
		break;
	default :
		code;
}

?>

loops

<?php

while(condition)
{
	code:
}

for ( $x=0 ; $x <= 10 ; $x++ )
{
	code ;
}

// foreach loop  = only used on array

foreach($array as $ value )
{
	code;
}

$color = array("red","green","blue");
foreach($color as $ value )
{
	echo "$ value <br>";
}

?>

functions

we use function keyword to declare functions

<?php

function Name()
{
	code ;
	return statement ;
}
?>

we can pass arguments also
we can also change return type
- return (type)($a); eg """ return(int)($a); """

arrays

array() ; - keyword is used , index start from x
count() ; = length of array
- count($array);
sort()
arrray_shift()
array_slice()
array_replace()
array_search()
array_pop()
ksort() - sort according to key , asc
rsort() - sort in des
asort() - acc to value in asc

// These are called indexed arrays:
$arr = array('this', 'that', 'what');
echo $arr[0];
echo $arr[1];
echo $arr[2]; 

// these are called associative arrays

$age = array("nitish" => "35" , "saini " => "25");
echo $age["peter"] ;

foreach( $age as $x => $x_value)
{
	echo $age ;
}

superglobal variables

predefined variables in php , accessible throught file

- $GLOBALS
- $_SERVER
- $_REQUEST
- $_POST
- $_GET
- $_FILES
- $_ENV
- $_COOKIE
- $_SESSION

$_GLOBAL - $GLOBALS is a PHP super global variable which is used to access global variables from anywhere in the PHP script (also from within functions or methods). PHP stores all global variables in an array called $GLOBALS[index]. The index holds the name of the variable.

<?php
$x = 75;
$y = 25;
 
function addition() {
  $GLOBALS['z'] = $GLOBALS['x'] + $GLOBALS['y'];
}
 
addition();
echo $z;
?>

$_SERVER is a PHP super global variable which holds information about headers, paths, and script locations
- $_SERVER['PHP_SELF'] Returns the filename of the currently executing script
- $_SERVER['GATEWAY_INTERFACE'] Returns the version of the Common Gateway Interface (CGI) the server is using
- $_SERVER['SERVER_ADDR'] Returns the IP address of the host server
- $_SERVER['SERVER_NAME'] Returns the name of the host server
- $_SERVER['SERVER_SOFTWARE'] Returns the server identification string (such as Apache/2.2.24)
- $_SERVER['SERVER_PROTOCOL'] Returns the name and revision of the information protocol (such as HTTP/1.1)
- $_SERVER['REQUEST_METHOD'] Returns the request method used to access the page (such as POST)
- $_SERVER['REQUEST_TIME'] Returns the timestamp of the start of the request (such as 1377687496)
- $_SERVER['QUERY_STRING'] Returns the query string if the page is accessed via a query string
- $_SERVER['HTTP_ACCEPT'] Returns the Accept header from the current request
- $_SERVER['HTTP_ACCEPT_CHARSET'] Returns the Accept_Charset header from the current request (such as utf-8,ISO-8859-1)
- $_SERVER['HTTP_HOST'] Returns the Host header from the current request
- $_SERVER['HTTP_REFERER'] Returns the complete URL of the current page (not reliable because not all user-agents support it)
- $_SERVER['HTTPS'] Is the script queried through a secure HTTP protocol
- $_SERVER['REMOTE_ADDR'] Returns the IP address from where the user is viewing the current page
- $_SERVER['REMOTE_HOST'] Returns the Host name from where the user is viewing the current page
- $_SERVER['REMOTE_PORT'] Returns the port being used on the user's machine to communicate with the web server
- $_SERVER['SCRIPT_FILENAME'] Returns the absolute pathname of the currently executing script
- $_SERVER['SERVER_ADMIN'] Returns the value given to the SERVER_ADMIN directive in the web server configuration file (if your script runs on a virtual host, it will be the value defined for that virtual host)
- $_SERVER['SERVER_PORT'] Returns the port on the server machine being used by the web server for communication (such as 80)
- $_SERVER['SERVER_SIGNATURE'] Returns the server version and virtual host name which are added to server-generated pages
- $_SERVER['PATH_TRANSLATED'] Returns the file system based path to the current script
- $_SERVER['SCRIPT_NAME'] Returns the path of the current script
- $_SERVER['SCRIPT_URI'] Returns the URI of the current page
$_REQUEST is a PHP super global variable which is used to collect data after submitting an HTML form

<html>
<body>

<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  // collect value of input field
  $name = $_REQUEST['fname'];
  if (empty($name)) {
    echo "Name is empty";
  } else {
    echo $name;
  }
}
?>

</body>
</html>

$_POST is a PHP super global variable which is used to collect form data after submitting an HTML form with method="post". $_POST is also widely used to pass variables

<html>
<body>

<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  // collect value of input field
  $name = $_POST['fname'];
  if (empty($name)) {
    echo "Name is empty";
  } else {
    echo $name;
  }
}
?>

</body>
</html>

$_GET is a PHP super global variable which is used to collect form data after submitting an HTML form with method="get".
$_GET can also collect data sent in the URL
to prevent hacker we use htmlspecialchars() function which converts < , > in &lt and &gt , also we trim() and , stripsplasehs to remove spaces and / etc

file handling

readfile (file) - is used to read file and output its content in buffer
fopen(file,mode)
fclose()
fread (file , bytes to read )

fread($myfile , filesize("File"))

fgets () - read single line
feof() - end of file , used for looping till end of file
fgetc() - get single character
fwrite (file,text to replace ) - used to write
modes in file
- r - read
- w - write , data is overwritten
- a - preserved and write (append)
- x - create new file for write only , false if exist
- r+ - read / write
- w+
- a+ - read / write
- x+ - read / write

cookie

A cookie is created with the setcookie() function

setcookie($cookie_name, value, expire, path, domain, secure, httponly);

Only the name parameter is required. All other parameters are optional.
to retrieve cookie
- $_COOKIE($cookie_name)

<?php
$cookie_name = "user";
$cookie_value = "Alex Porter";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/");
?>
<html>
<body>

<?php
if(!isset($_COOKIE[$cookie_name])) {
  echo "Cookie named '" . $cookie_name . "' is not set!";
} else {
  echo "Cookie '" . $cookie_name . "' is set!<br>";
  echo "Value is: " . $_COOKIE[$cookie_name];
}
?>

</body>
</html>

session

A session is a way to store information (in variables) to be used across multiple pages.
Unlike a cookie, the information is not stored on the users computer
A session is started with the session_start() function.
Session variables are set with the PHP global variable: $_SESSION
- $_SESSOIN[key] = value ; // stores session info
remove all session variables
- session_unset();
destroy the session
- session_destroy();

<?php
session_start();
?>
<!DOCTYPE html>
<html>
<body>

<?php
// to change a session variable, just overwrite it
$_SESSION["favcolor"] = "yellow";
print_r($_SESSION);
?>

</body>
</html>

The filter_var() function both validate and sanitize data from external source like cookies , forms ,inputs ,etc

php json

The json_encode() function is used to encode a value to JSON format.
The json_decode() function is used to decode a JSON object into a PHP object or an associative array

<?php

$cars = array("Volvo", "BMW", "Toyota");

echo json_encode($cars);

$jsonobj = '{"Peter":35,"Ben":37,"Joe":43}';

$obj = json_decode($jsonobj);

echo $obj->Peter;
echo $obj->Ben;
echo $obj->Joe;

$jsonobj = '{"Peter":35,"Ben":37,"Joe":43}';

$arr = json_decode($jsonobj, true);

echo $arr["Peter"];
echo $arr["Ben"];
echo $arr["Joe"];

$jsonobj = '{"Peter":35,"Ben":37,"Joe":43}';

$obj = json_decode($jsonobj);

foreach($obj as $key => $value) {
  echo $key . " => " . $value . "<br>";
}

?>

oops

-> is called object operator

class name {
	//properties
		public $name;
		public $color;
	
	//methods
	function set_name($name){
		$this->name = $ $name;
		return $this->name;
	}
}

$apple = new fruit();
echo $apple->set_name("apple");


// constructor 

__construct() , this fn is called when object created

function __construct($name){
	$this->name = $name;
}

$apple = new fruit("apple");

mysql db with php

we first need to connect , mysqli , i= improved
connect

// creating mysqli object 
$con= new mysqli($servername , usr ,pass)

// checking if connected 
if ($con -> connect_error){
	die("Conn fail" .$con->connect_error);
}

$con->close();

now after we have checked connection we can create db

$sql = "CREATE DATABAES mydb";

if($con->query($sql)==true){
	echo "sucess";
}
// we can pass all commands like this 
// we use same procedure to create tables and all those things 

// to send multiple query

$con ->multiquery($sql)

// querying data

$sql = "select id ,fname FROM mydb ";
$result = $con->query($sql);
if ($result ->num_rows >0 ){
	while ($row = $result->fetch_assoc()){
		echo row[id]
	}
}

// close all connections

num_rows() - check if more than zero rows returned
fetch_assoc() - puts all resultys into an associative array that we can loop through

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what is php ?

basic syntax

variables

data types

functions

arrays

superglobal variables

file handling

cookie

session

php json

oops

mysql db with php

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what is php ?

basic syntax

variables

data types

functions

arrays

superglobal variables

file handling

cookie

session

php json

oops

mysql db with php