PHP
Chapt.1 Basic Info
1. PHP files can include “html”, “CSS” and “JavaScript” code
2. Basic symbols
| Code | Description |
|---|---|
<?php ... ?> | Tags for PHP code |
; {} | Statement terminators |
// /*...*/ | Annotations |
$s | Define a variable “s” |
= | Assignment Operator |
Chapt.2 Output
1. PHP use echo and print to output contents:
<?php
echo 111,222; // Multiple
echo '<hr>';
print 111; // Single
echo '<hr>';
$a_zzy = 'Variable name cannot begin with a number and there cannot be spaces after the $';
echo $a_zzy;
?>
Chapt.3 Type of Data
1. Integer, float, boolean, null and string
<?php
$x = true;
var_dump($x); // "var_dump()" can print the type of a variable
$y = -123;
var_dump($y);
$f = 3.1415;
var_dump($f);
$s1 = '我是'; // The length of 1 Chinese character == 3 en characters
var_dump($s1);
$s2 = 'my name is Jay';
var_dump($s2);
$s3 = "$s1 zzy"; // " can parse variable content, while ' cannot
var_dump($s3);
$n = null;
var_dump($n);
?>
2. Array
<?php
$arr1 = array( // Or use "[]"
'ouyang',
'miejue'
);
echo $arr1[1],'<hr>';
$arr2 = [
'ouyang' => '欧阳',
'西门吹雪',
'东方不败'
];
echo $arr2['ouyang'],'<hr>'; // Custom array subscript
print_r($arr2); // Output the whole array
echo '<hr>';
$s1 = 'I am';
echo $s1.$arr1[1], '她叫', $arr2[1]; // "." and "," have the same effect
3. Multidimensional array (Try not to exceed 3 dimensions)
$MultiD_arr = array(
array(
'ouyang'
),
array(
'miejue'
),
array(
'ximen',
'kungfu'=>[
'PHP',
'Python',
'C++']
)
);
print_r($MultiD_arr); // Arrays of different dimensions can be nested together
echo '<hr>';
echo 'I can use'.$MultiD_arr[2]['kungfu'][1].', and am learning'.$MultiD_arr[2]['kungfu'][0]; // Access elements in multi-D array
4. Loops in array
foreach($arr2 as $k=>$v){ // Key "k" and value "v"
echo $v, $k;
echo '<hr>';
}
foreach($MultiD_arr as $k=>$v){ // It proves that we'd better not to define a mixed-dimensional array
foreach($v as $vv){
echo $vv;
}
}
?>
5. Constant
<?php
define('HOST', '127.0.0.1'); // Definition method 1
echo HOST;
const NAME = 'PHP website'; // Definition method 2
echo NAME;
?>
Chapt.4 Grammar
1. Conditional statements
<?php
// "?" and ":"
$str1 = 'ouyang';
echo $str1 ? 'I am ouyang' : 'Unknown';
// "if", "elseif" and "else"
$str2 = '';
$str3 = '1';
if($str2){
echo 'I have content';
}
elseif($str3){
echo "I have".$str3;
}
else{
echo 'Both are null';
}
// "switch"
switch($str1){
case 'ouyang':
echo 'I am ouyang';
break;
case 'miejue':
echo 'I am miejue';
break;
default:
echo $str1;
}
// PHP8 has "match()" to match and output in the form of key&value
$str4 = 'zzy';
echo match($str4){ // Exact match (while "switch" is not). For example, character number and integer number will be distinguished
'hht' => 'Haotian He',
'zzy' => 'Zhongyi Zheng',
'wj' => 'Jing Wang'
};
?>
2. Built-in functions
<?php
$ouyang = 'OUYANG';
echo strtolower($ouyang); // Convert to lowercase
$miejue = 'miejueshitai';
echo strtoupper($miejue); // Convert to uppercase
$php = 'ouyang, miejue, ximen';
print_r ( explode(',', $php) ); // Divide string into array by ","
$ximen = 'ximen';
echo md5($ximen); // Use "md5" to encrypt string
$arr = ['ouyang', 'ximen', 'tianpeng'];
echo count($arr); // Counting the number of elements
echo implode(',',$arr); // Combine array into string by ","
echo in_array('tianpeng', $arr); // Query the giving content
array_pop($arr); // Delete the last element
print_r($arr);
?>
3. Custom functions
<?php
$num2 = 13;
function num($num1, $num2){
//global $num2; //Use "global" to call global variables in functions
return $num1 * $num2;
}
echo num(12, 11);
?>
4. Operators
| Operator | Description |
|---|---|
| + | Add |
| - | Subtract |
| * | Multiply |
| / | Divide |
| % | Modular |
| ++ | Same as in C |
| – | Same as in C |
| == | Equal to |
| != | Not equal to |
| >= | Greater than or equal to |
| <= | less than or equal to |
| === | Identically equal to |
| !== | Not identically equal to |
| and | Logic and |
| or | Logic or |
| xor | Logic xor |
| ! | Logic not |
<?php
var_dump( 100 === 100 );
echo '<hr>';
var_dump( true === 'true' ); // "(Not) Identically equal to" compare not only values but also data types
?>
5. Loops
<?php
// "while"
$int = 1;
while($int < 10){
echo $int;
$int++;
}
// "do...while"
$int = 1;
do {
echo $int;
$int++;
}while($int < 10);
// "for"
$int1 = 1;
for($int1; $int1<10; $int1++){
if($int1 == 5){
echo '5';
}
else{
echo $int1;
}
}
?>
Chapt.5 Database
1. PHP could operate databases through the “PDO (PHP Data Object)”:
<?php
$pdo = new PDO('mysql:host=localhost;dbname=blog', 'root', 'root'); // PDO($dsn, $username, $password)
//var_dump($pdo);
$stmt = $pdo->prepare('select * from article'); // "->" calls the property of the class
$stmt->execute();
$arr = $stmt->fetchAll();
print_r($arr);
?>
2. Instruction about the Mysql database please refer to here
Chapt.6 Superglobal Variable
1. Use
- Superglobal variables can be used across pages. For example, they can be used directly in “test2.php” though created in “test.php”
| Superglobal variable | Description |
|---|---|
$_GET | Receive the value in the URL, which is displayed after “?” |
$_POST | Receive the value in the URL, but not be displayed |
$_COOKIE | Be used to identify users and stored in client browsers |
$_SESSION | Be used to store “sessions” and stored in servers |
$_REQUEST | Include the value of “get”, “post” and “cookie” |
$GLOBALS | A global combined array that includes all variables |
2. Example
<?php
// print_r($GLOBALS);
setcookie('user','admin');
print_r($_COOKIE);
echo '<hr>';
session_save_path("D:/");
session_start();
$_SESSION['user'] = 'admin';
print_r($_SESSION);
?>
<html>
<head>
<meta charset="utf-8" />
<title>PHP website</title>
</head>
<body>
<form action="" method="post">
lecturer: <input type="text" name="name" /> School:
<input type="text" name="school" />
<input type="submit" value="submit" />
</form>
</body>
</html>
Chapt.7 Class and Object
1. Three characteristics:
- Inheritance: Allows an object of one type to obtain the attributes and methods of an object of another type (the parent class cannot use the contents of the child class)
- Encapsulation: Abstracts an object into a class. Each class implements protection mechanisms for its own attributes and methods
- Polymorphism: Refers to that an entity has multiple forms at the same time, which is mainly embodied in the inheritance of the class (inherit first and then rewrite)
2. Class attribute and class method
<?php
class Teacher{
// Class attribute (variable)
public $name = 'ouyang'; // "public" (default): visible within class, outside class and in subclasses
protected $school = 'SWJTU'; // "protected": visible within class and subclasses, but invisible outside class
private $id_num; // "private": visible only within class, invisible in subclasses and outside class
// Method
public function fun1(){
echo 'Name：miejue, School: SCU<hr/>'; // Try not to use "echo" but "return" in class
}
public function fun2(){
return 'Name：miejue, School: SCU<hr/>';
}
public function fun3(){ // Use pseudo variable "$this" to refer to the variable of current class
return 'Name:'.$this->name.', School: '.$this->school.', ID Number: '.$this->id_num.'<hr/>';
}
public function fun4(){
return $this->fun3(); // Use pseudo variable "$this" to refer to the method of current class
}
// Magic methods (Only record "__construct" and "__destruct" here)
public function __construct($name, $school, $id_num){ // "__construct" is executed when instantiating
$this->name = $name;
$this->school = $school;
$this->id_num = $id_num;
}
public function __destruct(){ // "__destruct" is automatically executed after the class execution
echo 'Class executed, ready to be destructed<hr/>';
}
}
3. Inheritance and polymorphism
class PHPteacher extends Teacher{ // Inherit the class "Teacher" defined above
public function fun5(){
return $this->school;
}
public function fun6(){
return $this->id_num;
}
public function fun1(){
return 'I am rewritten here to embody the Polymorphism<hr/>';
}
}
// Some tests
$ximen = new Teacher('ximen','SCU','5101061998');
print_r($ximen);
echo '<hr/>';
echo $ximen->name;
echo '<hr/>';
echo $ximen->fun3();
$ouyang = new PHPteacher('ouyang','SWJTU','5101051997');
print_r($ouyang);
echo '<hr/>';
echo $ouyang->id_num; // Cannot access "id_num" (private)
echo '<hr/>';
echo $ouyang->fun5(); // Can access "school" (protected)
echo $ouyang->fun6(); // Still cannot access "id_num"
echo $ouyang->fun3();
echo $ouyang->fun1();
?>
4. Abstract class
- Abstract class cannot be instantiated but only inherited
- Abstract methods (no func body) in abstract class need to be rewritten in subclass
<?php
abstract class Teacher1 { // Notice that there is no "abstract attribute"
protected $name;
private $school;
public function __construct($name, $school) {
$this->name = $name;
$this->school = $school;
}
public function fun1() {
return 'Name: ' . $this->name . ', School: ' . $this->school .'<hr/>';
}
abstract public function fun2();
}
class PHPTeacher1 extends Teacher1 {
public function fun3() {
return $this->fun1();
}
public function fun2() {
return 'I am the rewritten method after inheriting <hr/>';
}
}
$obj = new PHPTeacher1('ximen', 'SCU');
echo $obj->fun2();
echo $obj->fun3();
?>
5. Interface
- Interface is a special kind of abstract class, and its methods are all abstract
<?php
interface file{
public function noTF($param); // Don't need to use the "abstract" keyword, but end its methods with ";"
public function noZY($param);
}
class Teacher2 implements file { // Use "implements" to implement an interface
protected $name;
private $school;
public $noTF;
public $noZY;
public function __construct($name, $school) {
$this->name = $name;
$this->school = $school;
}
public function noTF($param) {
$this->noTF = $param;
}
public function noZY($param) {
$this->noZY = $param;
}
public function fun1() {
return 'I am' . $this->name . ', ' . $this->noTF . $this->noZY;
}
}
$obj = new Teacher2('ouyang', 'SWJTU');
$obj->noTF('I didn't conduct corporal punishment on students, ');
$obj->noZY('I didn't assign any homework');
echo $obj->fun1();
?>
6. Namespace
- It is used to solve the naming conflict of global members, drawing on the idea of file directory (different directories can have files with the same name)
- The namespace must be written at the beginning of the program
- Except for variables, the rest members cannot be directly accessed across namespaces
<?php
namespace one;
const NAME = 'Constant of miejue <hr/>';
function php(){
return 'Function of miejue <hr/>';
}
class phpcn{
public function fun(){
return 'Class of miejue <hr/>';
}
}
// Access in namespace one
echo php();
echo \two\php();
echo \one\three\php();
use \one\three as t; // Use sub-namspace "one\three" and rename it with "as"
echo t\php();
namespace two;
const NAME = 'Constant of ximen <hr/>';
function php(){
return 'Function of ximen <hr/>';
}
class phpcn{
public function fun(){
return 'Class of ximen <hr/>';
}
}
namespace one\three; // Sub-namespace
const NAME = 'Constant of ouyang <hr/>';
function php(){
return 'Function of ouyang <hr/>';
}
class phpcn{
public function fun(){
return 'Class of ouyang <hr/>';
}
}
?>
Chapt.8 New Feature of PHP8
New feature 1: JIT compiler
- JIT (Just In Time) compiler can greatly improve the performance of PHP
- JIT compiler will be integrated into PHP as an extension. The “Opcache extension” is used to directly convert some opcodes into cpu instructions at runtime
- JIT is valid only when “Opcache” is enabled
New feature 2: You can assign variables with default values when calling functions
- PHP7
function test($a,$b=0,$c=0,$d=0){
echo $a;
echo '<hr/>';
echo $b;
echo '<hr/>';
echo $c;
echo '<hr/>';
echo $d;
}
test(10,20,30,40);
- PHP8
function test($a,$b=0,$c=0,$d=0){
echo $a;
echo '<hr/>';
echo $b;
echo '<hr/>';
echo $c;
echo '<hr/>';
echo $d;
}
test(10,20,d:30,c:40);
New feature 3: You can define and initialize attributes in the constructor at the same time
public function __construct(public $name, public $school, public $id_num){}