PHP

变量

<?php ... ?>—PHP opening/closing tags

$var = "value";—Variable (always $ prefix)

echo "text";—Output to browser

print_r($var);—Print readable info

var_dump($var);—Detailed type + value

define("CONST", val);—Define constant

const NAME = val;—Class constant

isset($var)—Check if set and not null

empty($var)—Check if empty/falsy

数组

string—Text type

int / float—Number types

bool—true or false

array—Array type

null—No value

gettype($var)—Get type name

(int) $var—Cast to integer

(string) $var—Cast to string

intval($str)—Parse integer

is_array($var)—Type check

字符串

"Hello $name"—Double-quote interpolation

'literal string'—No interpolation

strlen($s)—String length

strpos($s, "sub")—Find position

substr($s, start, len)—Substring

str_replace(old, new, $s)—Replace

explode(",", $s)—Split to array

implode(",", $arr)—Join array to string

trim($s)—Remove whitespace

strtolower($s) / strtoupper()—Case conversion

函数

$arr = [1, 2, 3];—Indexed array

$arr = ["k" => "v"];—Associative array

count($arr)—Array length

array_push($arr, $val)—Add to end

array_pop($arr)—Remove from end

array_merge($a, $b)—Merge arrays

array_map(fn, $arr)—Transform each element

array_filter($arr, fn)—Filter elements

in_array($val, $arr)—Check if value exists

array_keys($arr)—Get all keys

sort($arr) / asort($arr)—Sort by value

foreach ($arr as $k => $v)—Loop over array

数据库

function fn($a, $b) { }—Define function

fn($a, $b = 5)—Default parameter

function fn(int $a): string—Type hints

fn(...$args)—Variadic arguments

$fn = fn($x) => $x * 2;—Arrow function

class MyClass { }—Define class

new MyClass()—Create instance

$this->prop—Instance property

public / private / protected—Visibility

extends / implements—Inheritance / interface

Control Flow

if ($cond) { } else { }—If-else

switch ($val) { case: }—Switch statement

match ($val) { pat => result }—Match expression (8.0+)

for ($i=0; $i<$n; $i++)—For loop

foreach ($arr as $v)—Foreach loop

while ($cond) { }—While loop

$a ?? $b—Null coalescing

$a ?. method()—Nullsafe operator (8.0+)

Error Handling & I/O

try { } catch (Exception $e) { }—Try-catch

throw new Exception(msg)—Throw exception

finally { }—Always executes

file_get_contents($path)—Read file to string

file_put_contents($path, $d)—Write string to file

json_encode($data)—Convert to JSON

json_decode($json, true)—Parse JSON to array

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