PHP 知识点速查

<?php // 以 PHP 开放标签开头
echo "Hello World\n";
print("Hello jaywcjlove.github.io");
?>

PHP 运行命令

$ php hello.php

$boolean1 = true;
$boolean2 = True;
$int = 12;
$float = 3.1415926;
unset($float);  // 删除变量
$str1 = "How are you?";
$str2 = 'Fine, thanks';

查看: Types

$url = "jaywcjlove.github.io";
echo "I'm learning PHP at $url";
// 连接字符串
echo "I'm learning PHP at " . $url;
$hello = "Hello, ";
$hello .= "World!";
echo $hello;   # => Hello, World!

查看: Strings

$num = [1, 3, 5, 7, 9];
$num[5] = 11;
unset($num[2]);    // 删除变量
print_r($num);     # => 1 3 7 9 11
echo count($num);  # => 5

查看: Arrays

$x = 1;
$y = 2;
$sum = $x + $y;
echo $sum;   # => 3

查看: Operators

function add($num1, $num2 = 1) {
    return $num1 + $num2;
}
echo add(10);    # => 11
echo add(10, 5); # => 15

查看: Functions

# 这是一个单行 shell 样式的注释
// 这是一行 c++ 风格的注释
/* 这是一个多行注释
    另一行注释 */

const MY_CONST = "hello";
echo MY_CONST;   # => hello

# => MY_CONST is: hello
echo 'MY_CONST is: ' . MY_CONST; 

class Student {
  public function __construct($name) {
      $this->name = $name;
  }
}
$alex = new Student("Alex");

查看: Classes

echo 'this is a simple string';

查看: Strings

$arr = array("hello", "world", "!");

查看: Arrays

$float1 = 1.234;
$float2 = 1.2e7;
$float3 = 7E-10;
$float4 = 1_234.567;  // as of PHP 7.4.0
var_dump($float4);    // float(1234.567)
$float5 = 1 + "10.5";   # => 11.5
$float6 = 1 + "-1.3e3"; # => -1299

$a = null;
$b = 'Hello php!';
echo $a ?? 'a is unset'; # => a is unset
echo $b ?? 'b is unset'; # => Hello php
$a = array();
$a == null    # => true
$a === null   # => false
is_null($a)   # => false

function bar(): iterable {
  return [1, 2, 3];
}
function gen(): iterable {
  yield 1;
  yield 2;
  yield 3;
}
foreach (bar() as $value) {
  echo $value;   # => 123
} 

# => '$String'
$sgl_quotes = '$String';
# => 'This is a $String.'
$dbl_quotes = "This is a $sgl_quotes.";
# => a    tab character.
$escaped   = "a \t tab character.";
# => a slash and a t: \t
$unescaped = 'a slash and a t: \t';

$str = "foo";
// 未插值的多行
$nowdoc = <<<'END'
Multi line string
$str
END;
// 将执行字符串插值
$heredoc = <<<END
Multi line
$str
END;

$s = "Hello Phper";
echo strlen($s);       # => 11
echo substr($s, 0, 3); # => Hel
echo substr($s, 1);    # => ello Phper
echo substr($s, -4, 3);# => hpe
echo strtoupper($s);   # => HELLO PHPER
echo strtolower($s);   # => hello phper
echo strpos($s, "l");      # => 2
var_dump(strpos($s, "L")); # => false

另见: 字符串函数

$multiArray = [ 
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9],
];
print_r($multiArray[0][0]) # => 1
print_r($multiArray[0][1]) # => 2
print_r($multiArray[0][2]) # => 3

$arr = array(5 => 1, 12 => 2);
$arr[] = 56;      // 附加
$arr["x"] = 42;   // 用键添加
sort($arr);       // 排序
unset($arr[5]);   // 消除
unset($arr);      // 移除所有

查看: 数组函数

$array = array('a', 'b', 'c');
$count = count($array);
for ($i = 0; $i < $count; $i++) {
    echo "i:{$i}, v:{$array[$i]}\n";
}

$colors = array('red', 'blue', 'green');
foreach ($colors as $color) {
    echo "Do you like $color?\n";
}

$arr = ["foo" => "bar", "bar" => "foo"];
foreach ( $arr as $key => $value )
{
    echo "key: " . $key . "\n";
    echo "val: {$arr[$key]}\n";
}

$a = [1, 2];
$b = [3, 4];
// PHP 7.4 以后
# => [1, 2, 3, 4]
$result = [...$a, ...$b];

$array = [1, 2];
function foo(int $a, int $b) {
  echo $a; # => 1
    echo $b; # => 2
}
foo(...$array);

function foo($first, ...$other) {
  var_dump($first); # => a
    var_dump($other); # => ['b', 'c']
}
foo('a', 'b', 'c' /*, ...*/ );
// 或
function foo($first, string ...$other){}

:-	-
+	添加
-	减法
*	乘法
/	分配
%	取模
**	求幂

:-	-
a += b	如同 a = a + b
a -= b	如同 a = a – b
a *= b	如同 a = a * b
a /= b	如同 a = a / b
a %= b	如同 a = a % b

:-	-
==	平等的
===	完全相同的
!=	不相等
<>	不相等
!==	不相同
<	少于
>	比...更棒
<=	小于或等于
>=	大于或等于
<=>	小于/等于/大于

:-	-
and	和
or	或者
xor	独家或
!	不是
&&	和
||	或者

// 算术
$sum        = 1 + 1; // 2
$difference = 2 - 1; // 1
$product    = 2 * 2; // 4
$quotient   = 2 / 1; // 2
// 速记算术
$num = 0;
$num += 1;       // 将 $num 增加 1
echo $num++;     // 打印 1（评估后的增量）
echo ++$num;     // 打印 3（评估前的增量）
$num /= $float;  // 将商除并分配给 $num

:-	-
&	和
`	`
^	异或（异或）
~	不是
<<	左移
>>	右移

$a = 10;
$b = 20;
if ($a > $b) {
    echo "a is bigger than b";
} elseif ($a == $b) {
    echo "a is equal to b";
} else {
    echo "a is smaller than b";
}

$x = 0;
switch ($x) {
    case '0':
        print "it's zero";
        break; 
    case 'two':
    case 'three':
        // do something
        break;
    default:
        // do something
}

# => Does
print (false ? 'Not' : 'Does');
$x = false;
# => Does
print($x ?: 'Does');
$a = null;
$b = 'Does print';
# => a is unsert
echo $a ?? 'a is unset';
# => print
echo $b ?? 'b is unset';

$statusCode = 500;
$message = match($statusCode) {
  200, 300 => null,
  400 => '未找到',
  500 => '服务器错误',
  default => '已知状态码',
};
echo $message; # => 服务器错误

查看: Match

$age = 23;
$result = match (true) {
    $age >= 65 => 'senior',
    $age >= 25 => 'adult',
    $age >= 18 => 'young adult',
    default => 'kid',
};
echo $result; # => young adult

$i = 1;
# => 12345
while ($i <= 5) {
    echo $i++;
}

$i = 1;
# => 12345
do {
    echo $i++;
} while ($i <= 5);

# => 12345
for ($i = 1; $i <= 5; $i++) {
    echo $i;
}

# => 123
for ($i = 1; $i <= 5; $i++) {
    if ($i === 4) {
        break;
    }
    echo $i;
}

# => 1235
for ($i = 1; $i <= 5; $i++) {
    if ($i === 4) {
        continue;
    }
    echo $i;
}

$a = ['foo' => 1, 'bar' => 2];
# => 12
foreach ($a as $k) {
    echo $k;
}

查看: Array iteration

function square($x)
{
    return $x * $x;
}
echo square(4);  # => 16

// 基本返回类型声明
function sum($a, $b): float {/*...*/}
function get_item(): string {/*...*/}
class C {}
// 返回一个对象
function getC(): C { return new C; }

// 在 PHP 7.1 中可用
function nullOrString(int $v) : ?string
{
    return $v % 2 ? "odd" : null;
}
echo nullOrString(3);       # => odd
var_dump(nullOrString(4));  # => NULL

查看: Nullable types

// 在 PHP 7.1 中可用
function voidFunction(): void
{
  echo 'Hello';
  return;
}
voidFunction();  # => Hello

function bar($arg = '')
{
    echo "In bar(); arg: '$arg'.\n";
}
$func = 'bar';
$func('test'); # => In bar(); arg: test

$greet = function($name)
{
    printf("Hello %s\r\n", $name);
};
$greet('World'); # => Hello World
$greet('PHP');   # => Hello PHP

function recursion($x)
{
    if ($x < 5) {
        echo "$x";
        recursion($x + 1);
    }
}
recursion(1);  # => 1234

function coffee($type = "cappuccino")
{
    return "Making a cup of $type.\n";
}
# => 制作一杯卡布奇诺
echo coffee();
# => 制作一杯
echo coffee(null);
# => 制作一杯浓缩咖啡
echo coffee("espresso");

$y = 1;
 
$fn1 = fn($x) => $x + $y;
// 相当于按值使用 $y：
$fn2 = function ($x) use ($y) {
    return $x + $y;
};
echo $fn1(5);   # => 6
echo $fn2(5);   # => 6

class Student {
    public function __construct($name) {
        $this->name = $name;
    }
    public function print() {
        echo "Name: " . $this->name;
    }
}
$alex = new Student("Alex");
$alex->print();    # => Name: Alex

class ExtendClass extends SimpleClass
{
    // 重新定义父方法
    function displayVar()
    {
        echo "Extending class\n";
        parent::displayVar();
    }
}
$extended = new ExtendClass();
$extended->displayVar();

class MyClass
{
    // 对象被视为字符串
    public function __toString()
    {
        return $property;
    }
    // 与 __construct() 相反
    public function __destruct()
    {
        print "Destroying";
    }
}

interface Foo 
{
    public function doSomething();
}
interface Bar
{
    public function doSomethingElse();
}
class Cls implements Foo, Bar 
{
    public function doSomething() {}
    public function doSomethingElse() {}
}

try {
    // 做一点事
} catch (Exception $e) {
    // 处理异常
} finally {
    echo "Always print!";
}

$str = "Visit jaywcjlove.github.io";
echo preg_match("/qu/i", $str); # => 1

查看: PHP中的正则表达式

:-	-
r	读
r+	读写，前置
w	写入，截断
w+	读写，截断
a	写，追加
a+	读写，追加

define("CURRENT_DATE", date('Y-m-d'));
// 一种可能的表示
echo CURRENT_DATE;   # => 2021-01-05
# => CURRENT_DATE is: 2021-01-05
echo 'CURRENT_DATE is: ' . CURRENT_DATE;