datetime
To string format
$dt_str=”2021–08–21 10:30:20";
echo (date(“Y-m-d H:i:s”, strtotime($dt_str)).”<br/>”);
echo (date(“Y-m-d h:i:sa”, strtotime($dt_str)).”<br/>”);
echo (date(“l”, strtotime($dt_str)).”<br/>”); // day of week
Add days/months/hours
echo (date(‘Y-m-d H:i:s’, strtotime($dt_str. ‘ + 2 days’)).”<br>”);
echo (date(‘Y-m-d H:i:s’, strtotime($dt_str. ‘ + 3 hours’)).”<br>”);
echo (date(‘Y-m-d H:i:s’, strtotime($dt_str. ‘ — 40 minutes’)).”<br>”);
echo (date(‘Y-m-d H:i:s’, strtotime($dt_str. ‘ — 2 months’)).”<br>”);
Get Now datetime
$now = date(“Y-m-d H:i:s”);
get date or time
$dt = strtotime(“2020–01–29 16:30:11”);
//date time
echo (date(“Y-m-d”,$dt).’<br>’);
//time part
echo(date(“H:i:s”,$dt));
compare date
$d1 = new DateTime(‘2020–08–03 14:52:10’);
$d2 = new DateTime(‘2020–01–03 11:11:10’);
var_dump($d1 == $d2);
var_dump($d1 > $d2);
var_dump($d1 < $d2);
Unix timestamp
$datetime = new DateTime(“2020–08–01 14:20:32”);
echo $datetime->getTimestamp();
//or
echo(time())
Timezone
Get all timezones
$timezone_identifiers = DateTimeZone::listIdentifiers();
foreach($timezone_identifiers as $key => $list){
echo $list . “<br/>”;
}
Set timezone
date_default_timezone_set(‘Europe/London’);
$now = date(“Y-m-d H:i:s”);
echo($now.’<br>’);
date_default_timezone_set(‘Indian/Kerguelen’);
$now = date(“Y-m-d H:i:s”);
echo($now.’<br>’);
Php map/filter/reduce
$users = [
[ ‘id’ => 1, ‘name’ => ‘a’ ],
[ ‘id’ => 2, ‘name’ => ‘b’ ],
[ ‘id’ => 3, ‘name’ => ‘c’ ]
];
function getNames(array $users, $id_after)
{
$filtered = array_filter($users, function ($x) use ($id_after) {
return $x[‘id’] > $id_after;
});
return array_map(function ($x) { return $x[‘name’]; }, $filtered);
}
$res = getNames($users ,1);
echo (json_encode($res).’<br>’);
function sum_id($users){
$id_arr = array_map(function($x){return $x[‘id’];} ,$users);
return array_reduce($id_arr, function ($sum, $cur) {
return $sum+$cur;
});
}
echo (sum_id($users).’<br>’);
Include and require
Require :if file does not exist throw error
include : continue execute even file does not exist
HTTP
get http GET parameter
$_GET[“name”]
get http POST parameter
$_POST[“name”]
get http POST json body
$json = file_get_contents(‘php://input’);
$data = json_decode($json);
upload file
if ($_FILES[‘uploadedfile’][‘error’] == UPLOAD_ERR_OK
&& is_uploaded_file($_FILES[‘uploadedfile’][‘tmp_name’])) {
echo file_get_contents($_FILES[‘uploadedfile’][‘tmp_name’]);
}
get client ip address
$ip = $_SERVER[‘HTTP_CLIENT_IP’] ? $_SERVER[‘HTTP_CLIENT_IP’] : ($_SERVER[‘HTTP_X_FORWARDED_FOR’] ? $_SERVER[‘HTTP_X_FORWARDED_FOR’] : $_SERVER[‘REMOTE_ADDR’]);
echo ($ip);
server variables
echo(json_encode($_SERVER));.
‘SERVER_ADDR’:The IP address of the server
‘REQUEST_METHOD’:GET/POST/PUT/DELETE
‘REQUEST_TIME’:timestamp when request hit server
‘QUERY_STRING’
‘HTTP_ACCEPT’
‘HTTP_ACCEPT_ENCODING’
‘HTTP_HOST’:full content of the post
‘HTTP_USER_AGENT’
‘HTTPS’: if this request using https
‘REMOTE_ADDR’:ip address of request pc
‘REMOTE_HOST’:host name of request pc
‘REMOTE_PORT’:client pc port
‘SERVER_PORT’
Get cookie
$_COOKIE[$cookie_name]
File/Folder
Read
//read all content
Readfile(‘sample.txt’)
//open then readall
$myfile = fopen(“test.txt”, “r”) or die(“Unable to open file!”);
echo fread($myfile,filesize(“test.txt”));
fclose($myfile);
//read by line
$myfile = fopen(“test.txt”, “r”) or die(“Unable to open file!”);
while(!feof($myfile)) {
echo fgets($myfile) . “<br>”;
}
fclose($myfile);
//read by char
$myfile = fopen(“test.txt”, “r”) or die(“Unable to open file!”);
while(!feof($myfile)) {
echo fgetc($myfile);
}
fclose($myfile);
Write
$myfile = fopen(“test1.txt”, “w”) or die(“Unable to open file!”);
$txt = “abc\n”;
fwrite($myfile, $txt);
$txt = “123\n”;
if (file_exists($myfile)) {
echo “Sorry, file already exists.”;
return;
}
fwrite($myfile, $txt);
fclose($myfile);
get current directory
echo (getcwd());
get directory file/folders
$res = scandir(‘/home’);
echo(json_encode($res));
Other useful methods
basename ($path) get filename
fseek() Seeks in an open file
fgetcsv() Returns a line from an open CSV file
file() Reads a file into an array
fileatime() Returns the last access time of a file
file_exists() Checks whether or not a file or directory exists
filectime() Returns the last change time of a file
filemtime() Returns the last modification time of a file
touch() Sets access and modification time of a file
unlink() Deletes a file
fileowner() Returns the user ID (owner) of a file
fileperms() Returns the file’s permissions
filesize() Returns the file size
filetype() Returns the file type
is_dir() Checks whether a file is a directory
is_file() Checks whether a file is a regular file
is_readable() Checks whether a file is readable
is_uploaded_file() Checks whether a file was uploaded via HTTP POST
is_writable() Checks whether a file is writable
stat() Returns information about a file
Object Oriented
Class
class Person {
//like most OO languages ,php support private,protected,public
// Properties
public $name;
public $id;
//constructor
function __construct($name) {
$this->name = $name;
}
// Methods
protected function set_name($name) {
$this->name = $name;
}
public function get_name() {
return $this->name;
}
function __destruct() {
echo “this method will be called when script is stopped or exited”;
}
}
Inheritance
class student extends person {
…
}
Abstract Class
abstract class parent {
abstract public function someMethod1();
abstract public function someMethod2($param1, $param2);
abstract public function someMethod3() : string;
}
class child: parent{
public function someMethod1(){…}
public function someMethod2($param1, $param2){…}
public function someMethod3() : string{…}
}
Interface
interface InterfaceName {
public function someMethod1();
public function someMethod2($param1, $param2);
public function someMethod3() : string;
}
class someClass: implements InterfaceName{
public function someMethod1(){…}
public function someMethod2($param1, $param2){…}
public function someMethod3() : string{…}
}
static
class sample{
public static function staticMethod(){
echo (“static method <br>”);
}
public static $staticProp = “abcd1234”;
}
sample::staticMethod();
echo(sample::$staticProp.”<br>”);
Trait
trait printMsg1 {
public function msg() {
echo “msg from trait1 “;
}
}
trait printMsg2 {
public function msg() {
echo “msg from trait2 “;
}
}
class Welcome {
use printMsg1;
//uncomment to raise error because trait method conflict
//use PrintMsg2;
// uncomment , class will override trait implementation
//public function msg(){
// echo (“msg from class”);
//}
}
$obj = new Welcome();
$obj->msg();
namespace
<?php
namespace namespace1;
class c1{
public static function print1(){
echo (“namespace1 function<br/>”);
}
}
?>
<?php
namespace namespace1\sub;
class c11{
public static function print1sub(){
echo (“namespace1 sub function<br/>”);
}
}
?>
<?php
namespace namespace2;
class c2{
public static function print2(){
echo (“namespace2 function<br/>”);
}
}
?>
<?php
use namespace1 as ns1;
ns1\c1::print1();
ns1\sub\c11::print1sub();
use namespace2 as ns2;
ns2\c2::print2();
?>
Error/Exception
log errors into error file
config : ‘error_log’ = some ‘path’ , log_errors=’1’
method : error_log(‘some error’);
Exception
getFile() : path of where exception thrown
getCode(): code that thrown exception
getLine(): line of code where exception thrown
getMessage(): exception description
getPrevious(): previous exception
getTraceAsString()/getTrace(): call stack
