PHP basic

Major websites that use PHP
Facebook, Flickr, Wikipedia, SugarCRM, Dotproject, Drupal, Interspire

php settings file: php.ini  (use phpinfo(); to show it's content)

Constants (can only defined once)
define("SYS_OWNER", "someone");
define("SYS_OWNER", "anotherone");   //this will raise error

Superglobal arrays: _COOKIE, _SESSION, _GET

Cookies
setcookie("cookieName", $val, time()+60*60*24);
$cookieVal = $_COOKIE["cookieName"];

Session (browser tabs are treated as same session)
session_start();
$_SESSION['today'] = date("Y-m-d");
$retrieveSessionVal = $_SESSION['today'];

Form Data
var variableVal = $_GET["variableName];
var variableVal = $_POST["variableName];
var variableVal = $_REQUST["variableName"];  //will return value set by all GET/POST/REQUEST, if of same name, precedence base on setting in php.ini directive "variable_order", say GPC, means Cookie taking precedence over Post, which take precedence over Get.

Function using default value:
function getRate($param1 = 10, $param2 = 15){ };

Pass by reference
function getRate(&$rate) { };

Include & Require
   include "some_lib.php";
which is same as:
   require "some_lib.php";
except that if file being include is absent, the latter will raise error while the former will not.

include_once "some_lib.php";
require_once "some_lib.php";

built-in functions: http://php.net/manual/en/indexes.functions.php

var_dump() - dump info of variable

String
HEREDOC construct:
$string = <<;< "RightHere"
Once upon a time, Sally's mother said "My dear"....
.......
RightHere;

NOWDOC: without resolution of variable content. differentiate from HEREDOC by the single quote
$string = <<;< 'RightHere'
Once upon a time, $someone mother said "My dear"....
.......
RightHere;

String Function (Best of)
trimming: ltrim, rtrim, trim
upper/lower case: strtoupper, strtolower

string length: strlen
word count: str_word_count
search string: strstr, stristr (case insensitive), strpos, str_replace
string modification: strip_tags, addslashes, stripslashes, str_shuffle, md5
html encode/decode(< to &lt;): htmlentities, html_entity_decode

pattern matching: preg_match
string substitution: preg_replace
string splitting: preg_split

Array
indexed array:
        $myarray[0]=1; $myarray[1]=2;
associative array:
        $myarray['first'] = 1; $myarray['second'] = "B"; 
    $myarray = array('first' =>1, 'second' =>'B');
traversing array:
        foreach($myarray as $key => $value){...}

Datetime function

$timezone = ini_get('data.timezone');   //get time zone from server's .ini file
$dtz = new DateTimeZone($timezone);
$dt = new DateTime('2015-02-03 16:33:22', $dtz);
$dt->format('Y-m-d h:i:s');

Array Function (Best of)
array_splice, e.g.:
    $array1 = array('first'=>1, 'second'=>2, 'third'=>3, 'fourth'=>4, 'fifth'=>5, 'sixth'=>6);
    $array2 = array_splice($array1, 2, 3);  //extract 3 element start from position 2
outcome:  
    $array1 = array('first'=>1, 'second'=>2, 'sixth'=>6);
    $array2 = array('third'=>3, 'fourth'=>4, 'fifth'=>5);
unset, e.g.:
    unset($array1['third']); //simply extract and remove element of key 'third'

sorting: sort (sort by value and reissue key sequentially), rsort, asort(sort by value), arsort (reverse), ksort (sort by key), krsort (reverse), usort (sorty by self-defined funciton)

math-type function: array_sum, count

array_unique (identify & remove duplication), array_rand (random), shuffle, array_merge
searching: in_array, array_search
extract (extract array elements to variables)

array_walk (apply function on every element of the array) e.g.
      array_walk($testgrade, 'add10'); //add10 is the function which add 10 to incoming value

Object
e.g. in myClass.inc :

class myClass{
    private $tag;
    function __construct(){...} //magic method: trigger each time the class is instantiated
    public function Begin(){ ...}
} //end class
$myclass = new myClass();
$myclass->Begin();

Database Interface
1. MySQLi (i stands for improved extension)

$mydb = new mysqli('localhost', 'username', 'password', 'dbname');
$sql = 'select * from guests';
$result = $mydb->query($sql);
while( $row = $result->fetch_assoc() ){ echo $row['lastname']; }
$result->close();
$mydb->close();

2. PDO - PHP data object (work with almost all kinds of database: MSSQL, MySQL, Oracle, SQLite, etc.)

configuration: add following in php.ini
  extension=php_pdo.dll
  extension=php_pdo_mysql.dll

$dsn = 'mysql:dbname=website;host=localhost';
$mypdo = new PDO($dsn, 'username', 'pwd');
$sql = 'select * from guests';
$result = $mypdo->query($sql);
while( $row = $result->fetch(PDO::FETCH_ASSOC) ){ echo $row['lastname']; }
$result->close();
$mypdo->close();

or use prepared statement:

$statement = $mypdo->prepare('select * from guests order by ?');
$mypdo->execute('lastname');

Session
 session_start();
 $lastInput = $_SESSION['lastInput'];

Other built-in function in PHP
mail() - sending email, require('class.phpmailer.php');
fpdf - generate pdf file, require('../../fpdf/fpdf.php');
jpgraph - generate graphical report, require('../../jpgraph/jpgraph.php');
captchas - generate antispam image, require('../../jpgraph/jpgraph_antispam.php');

working with XML 
$xml_doc = new SimpleXMLElement($xml_data);


Security
1. Escape output, so that someone can't leave a hyperlink in ur site
 htmlspecialchars($string, ENT_QUOTES);

2. Cross-site scripting, e.g. input <script> alert('hello');</script> in search box;

3. SQL injection

4. password encryption
use sha1:  sha1($string);
salt & pepper encryption:
  sha1(sha1($salt).$string_to_encrypt.sha1($pepper));   //where $salt & $pepper are hard-coded values

5. Security tips on PHP

• - turn off error display in php.ini
• - make sure register_globals is turned off in php.ini (register_globals create variables in memory based on a submitted HTML form)
• - use SSL where required
• - keep included lib, SQLite files and settings files outside document root

for more, read Chris Shiflett's Essential PHP Security

IDE: Komodo, Zend Studio for Eclipse, PhpED


get current time
               $current_time_int = time();
display in formatted string:
              $formatted_time = format_date(time(),'short');