PHP学习笔记

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PHP学习笔记（暂时先不更了…）

PHP Basic Rules

PHP文件默认的文件拓展名.php

The first PHP examle

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<!DOCTYPE html>
<html>
<body>

<h1>My first PHP page</h1>

<?php
echo "Hello World!";
?>

</body>
</html>

The function is to print “Hello World!” to Browser.Each line ends with ;

annotate(注释)

Like C, PHP have two ways to annotate.

  • 单行注释，use // or #
  • 多行注释，use /* */

Variables

  • in PHP, variable must begin with $
  • Variable names are case-sensitive($a and $A are different variables)
  • Other rules of name are the same as C language
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<?php
$text="Hello world!";
$a=1;
$b=2.5;
?>

We notice that PHP is Implicit type conversion(弱类型定义语言)

PHP 有四种不同的变量作用域：

  • local
  • global
  • static
  • parameter

If we want to visit global variables in function, we must use global

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<?php
$x = 1;
$y = 2;

function sumOfTwo()
{
    global $x, $y;
    $x = $x + $y
}

sumOfTwo();
echo $x;
?>

PHP stores all global variable in an array named $GLOBALS[index], index is the name of variable. It can be visited in function.

When a function completes, it’s all variables will be delete. However, sometimes you hope the variable can be saved. To do it, you can use static when declaring the variable.

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static $x=0;

$x is still a local variable!

Echo

  1. multiple parameter

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    <?php
    echo "Hello world!<br>";
    echo "This is ", "a string,", "which use ", "multiple ", "parameter.";
    ?>

  2. With variables

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    echo "在 $txt2 学习 PHP ";
    echo "<br>";
    echo "我车的品牌是 {$cars[0]}";

Difference between echo and print

  • echo - 可以输出一个或多个字符串
  • print - 只允许输出一个字符串，返回值总为 1
  • 其他方面相似，都可以输出with variables

Tips：echo is faster than print， echo have no return value ，print return 1。

Data Type

  • String -> We can put any word in '' or ""
  • Integer -> 十六进制（ 以 0x 为前缀）或八进制（前缀为 0）
  • Float
  • Boolean(true, false)
  • Array
  • Object（对象）
  • NULL（空值）
  • Resource（资源类型）
Array
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<?php
$cars=array("Aito","BMW");  
?>
Object
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<?php
class Car
{
    var $color;
    function __construct($color="green"){
        $this->color = $color;
    }
    function what_color(){
        return $this->color;
    }
}
?>
Resource

resource is a special variable, which stores a refrence to outer resource

(link to database、open the file…)

Comparison of data

  • Loose comparison：use==, only compare the value of variables
  • Strict comparison：use===，not only value,but also type。

字符串在进行比较时，会转化成数字进行数学比较！

Const

usedefine() ：

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bool define ( string $name , mixed $value [, bool $case_insensitive = false ] )

three parameter:

  • name
  • value
  • case_insensitive ：optional. If case_insensitive is TRUE，The constant is not case sensitive. The default is case-sensitive.

Example:

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define("BAIDU", "www.baidu.com");

String

并置运算符.

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<?php
$txt1="Hello world!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>

. in PHP is similar to + in C++(string)

Other string functions:

  1. strlen(), return the length of string
  2. strpos($s1, $s2), return the $s2 ‘s position in $s1

(String subscripts start at 0)

Structured programming

operator

  • +,-,*,/,%,~ is like C

  • intdiv(10, 3) === 3

  • we can use x += y , x++

  • both != and <> is legal
  • x!==y means 如果 x 不等于 y，或它们类型不相同，则返回 true
  • both and and && is legal(优先级不同)
  • <<,>>

If-else, switch

In php, if-else and switch are the same as that in C/C++.

The only difference is php provide elseif.

Example:

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<?php
$t=date("H");
if ($t<"10") {
    echo "Have a good morning!";
}
elseif ($t<"20") {
    echo "Have a good day!";
}
else {
    echo "Have a good night!";
}
?>

For、While

For
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<?php
for ($i = 1; $i <= 10; $i++)
{
    echo "数字为 " . $i . PHP_EOL;
}
?>
For each

Format 1:foreach ($array as $value){}

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<?php
$x = array("Google","Baidu","Bing");
foreach ($x as $value)  // x is the name of array
{
    echo $value . PHP_EOL;
}
?>

Format 2:foreach ($array as $key => $value){}

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<?php
$x = array(1=>"Google", 2=>"Baidu", 3=>"Bing");
foreach ($x as $key => $value)
{
    echo "key  为 " . $key . "，对应的 value 为 ". $value . PHP_EOL;
}
?>
While/Do While

In php, while and do while are the same as that in C/C++.

Format:while(condition){// some codes}

Array

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<?php
$s = array("aaa", "bbb", "abc");
echo count($s); // count() return the length of array
?>

Key-value:

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<?php
$age = array("Mike" => "35", "Amy"=>"37");
echo "Mike is ". $age['Mike'];
?>

sort

example:

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<?php
$s = array("aaa", "bbb", "abc");
sort($s);
?>

说明：

  • sort():对数组升序排列
  • rsort(): 对数组降序排列
  • ksort() : 根据关联数组的键，对数组升序排列
  • asort() :根据关联数组的值，对数组升序排列
  • krsort():根据关联数组的键，对数组降序排列
  • arsort() :根据关联数组的值，对数组降序排列

Function

Format

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<?php
function functionName($a, $b)
{
    $total = $a + $b
    return $total;
}
?>

php function uses return to return value