php
<?php xxx?>
1.case-sensitivity
The following are case-insensitive in PHP:
PHP constructs such as if, if-else, if-elseif, switch, while, do-while, etc.
Keywords such as true and false.
User-defined function & class names.
On the other hand, variables are case-sensitive. e.g., $message and $MESSAGE are different variables.
2.Variables
$name="alex";
$_sex=1;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<?php
$title="this is title";
?>
<h1><?php echo $title;?></h1>
<h1><?=$title;?></h1>
</body>
</html>
3.Constant
if(condition){
define(var,val);
}
ex: define('ORIGIN',[0,0])
or
const TAX=0.23;
Second, the define() function allows you to define a constant with the name that comes from an expression
<?php
define('PREFIX', 'OPTION');
define(PREFIX . '_1', 1);
define(PREFIX . '_2', 2);
define(PREFIX . '_3', 3);
4.Var_dump /die /function
<?php
function d($data){
echo '<pre>';
var_dump($data);
echo '</pre>';
}
function dd($data){
echo '<pre>';
var_dump($data);
echo '</pre>';
die();
}
// store the variables
$title="PHP is awesome";
$name="Alexmaodali";
$age=33;
d($name);
// dd($name);
echo 'after die';
require 'index.view.php';
5.Data Types
Scalar:Boolean Integer Float String
Compund:Array Object
Special:Null Resource
PHP treats the following values as false:
The false keyword.
The integer 0 and -0 (zero).
The floats 0.0 and -0.0 (zero).
The empty string ("", '') and the string “0”.
The empty array (array() or []).
The null.
The SimpleXML objects created from attributeless empty elements.
$max=1;
$price=2.3;
$is_admin=true;
$goods=['mouse','php']//
echo $goods[0];//mouse
also:
$prices=[
'pc'=>3000,
'tomato'=>1,
];
$price['pc'];//3000;
is_bool(var)
is_int(var);
PHP_INT_SIZE
PHP_INT_MIN
PHP_INT_MAX
0.123E1
$total=0.1+0.1+0.1;
echo $total==0.3;//flase
String
$name="Alex";
echo 'hello'.$name;//hello Alexjj
echo 'hello $name';//hello $name;
echo "hello $name";
echo "hello {$name}";//hello Alex
echo $name[0];//A
echo strlen($name);//4
heredoc:
$final=<<<EDD
hello $name;
EDD;
newdoc:will not expand the var
$final=<<<'EDD'
hello $name;
EDD;
null
$phone=null;
var_dump($phone);//NULL
$name='Alex'
unset($name);
var_dump($name);//NULL
var_dump(is_null($name));//true
var_dump($name===null);//bool(true);
type casting
(array)
(bool)
(int)
(float)
(object)
(string)
echo (int)12.8;//12
echo (int)'he';//0
echo (int)'100 USD';//100
echo (int)null;//0
echo (string)true;//1
echo (string)false;//''
echo (string)[1,3];//Array;
type juggling
$age=33;
$name='33';
if(age==name){
echo "age=name";//age=name
}
echo age+name;//66;
$d='33 sd';
echo age+name;//66;
6.if/for/while
<?php if ( expession) : ?>
<!-- HTML code here -->
<?php endif; ?>
if..elseif
if(xxx){
}elseif(xxx){
}
$a=10;
$b=12;
if($a>$b):
echo "a>b";
elseif($a<$b):
echo "a<b";
else:
echo 'a=b';
endif;
$result = $initial ?: $default;
$result='true'?:3;//true
<?php
switch (expression) {
case value1:
// code block 1
break;
case value2:
// code block 2
break;
case value3:
// code block 3
break;
default:
// default code block
}
<?php
for (start; condition; increment) {
statement;
}
while
<?php
while (expression):
statement;
endwhile;
<?php
while (expression)
statement;
7.function
<?php function welcome_user($username) { ?>
<span>Welcome <?= $username ?></span>
<?php } ?>
function name(a='alex',b){
xxx
}
Separate parameters by a comma (,). Since PHP 8.0, the parameter list can have the trailing comma (,) which the PHP interpreter ignores.
By default, arguments are passed by value in PHP.
Prepend parameters by an ampersand (&) to pass arguments by reference.
Named parameters
function cot($text,$name){
return $name.$text;
}
cot(
$text:'Alex',
"maodali"
);
PHP has four types of variable scopes including local, global, static, and function parameters.
type hint
function upper(?string str,mixed name):string|int
{
...
}
strict mode
declare(strict_types=1);
variable funcargs
function sum(){
$number=func_get_args();
...
}
function sum(...$num){
...
}
function sun(int $a,int $b,int ...$num){
...
}
Anonymous Function
$msg='hello';
$sayhi=funcion() use ($msg){
echo $msg;
}
Variable Functions
<?php
$f = 'strlen';
echo $f('Hello');//5
8.Array
$arr=array()
$arr=array(1,2)
$arr=[]
$arr=[1,2]
print_r($arr)
add an element:
$arr[]=1;
remove array element:
unset($arr[1])
Associate array:
$html=[]
$html['title']='php';
print_r($html['title'])
Foreach:
foreach($array_name as $element)..
foreach($array_name as $key=>$value)...
9.GET POST
$src=$_GET['name'];
10.Mysql
localhost/phpmyadmin/