## 匿名函數 ```php // Example1 $func = function( $param ) { echo $param; }; $func( 'some string' );//輸出：some string // Example2 function callFunc( $func ) { $func( 'some string' ); } $printStrFunc = function( $str ) { echo $str; }; callFunc( $printStrFunc ); //可以直接將匿名函數進行傳遞。如果你了解js，這種寫法可能會很熟悉 callFunc( function( $str ) { echo $str; } ); ``` ## 閉包 PHP在默認情況下，匿名函數內不能調用所在代碼塊的上下文變量，而需要通過使用use關鍵字。 ```php //1. 通過閉包獲取當前函數環境外的變量值副本。 function getMoney() { $rmb = 1; $dollar = 6; $func = function() use ( $rmb ) { echo $rmb; //1 echo $dollar; //報錯，找不到dorllar變量 }; $func(); } getMoney(); //2. 之所以稱為副本，是因為通過閉包傳值到匿名函數內的變量,值也是不能改變。 function getMoney() { $rmb = 1; $func = function() use ( $rmb ) { $rmb += 2; echo $rmb; // 3 }; $func(); echo $rmb; // 還是1沒有改變; } getMoney(); //3. 如果要改變外部變量的值，還是得通過傳址的方法 function getMoney() { $rmb = 1; $func = function() use ( &$rmb ) { $rmb += 2; echo $rmb; // 3 }; $func(); echo $rmb; // 3; } getMoney(); //4. function getMoneyFunc() { $rmb = 1; $func = function() use(&$rmb){ echo $rmb; //把$rmb的值加1 $rmb++; }; return $func; // 如果將匿名函數返回給外界，匿名函數會保存use所引用的變量，而外界則不能得到這些變量，這樣形成‘閉包’ } $getMoney = getMoneyFunc(); $getMoney(); // 1 $getMoney(); // 2 $getMoney(); // 3 ``` ### 閉包的好處 **1. 減少循環** ```php // 一個基本的購物車，包括一些已經添加的商品和每種商品的數量。 // 其中有一個方法用來計算購物車中所有商品的總價格。該方法使用了一個closure作為回調函數。 class Cart{ const PRICE_BUTTER = 1.00; const PRICE_MILK = 3.00; const PRICE_EGGS = 6.95; protected $products = array(); public function add($product , $quantity) { $this->products[$product] = $quantity; } public function getQuantity($product) { return isset($this->products[$product]) ? $this->products[$product] : false; } public function getTotal($tax) { $total = 0.00; // 使用閉包減少循環; $callback = function($quantity , $product) use ($tax , &$total){ $pricePerItem = constant(__CLASS__ . "::PRICE_" . strtoupper($product)); $total += ($pricePerItem * $quantity) * ($tax + 1.0); }; array_walk($this->products , $callback); return round($total , 2);; } } $my_cart = new Cart; // 往購物車里添加條目 $my_cart->add('butter' , 1); $my_cart->add('milk' , 3); $my_cart->add('eggs' , 6); // 打出出總價格，其中有 5% 的銷售稅. print $my_cart->getTotal(0.05) . "\n"; // The result is 54.29 ``` **2. 減少函數的參數** ```php function html($code , $id = "" , $class = "") { if ($id !== "") $id = " id = \"{$id}\""; $class = ($class !== "") ? " class =\"$class\"" : ""; $open = "<$code$id$class>"; $close = "</$code>"; return function($inner = "") use ($open , $close){ return "$open$inner$close"; }; } $tag = html('div','','class'); // 可讀性和可維護性大大提高; echo $tag('div1,div1,div1'); echo PHP_EOL; echo $tag('div2,div2,div2'); ``` **3. 解除遞歸函數** ```php // ↓↓ 注意,這里的fib一定要用引用哦,因為第一次的時候就會Notice: Undefined variable,然后后面的fib()就會錯誤; $fib = function($n) use (&$fib){ if ($n == 0 || $n == 1) return 1; return $fib($n - 1) + $fib($n - 2); }; echo $fib(2) . "\n"; // 2 $lie = $fib; $fib = function(){ die('error'); };//rewrite $fib variable echo $lie(5); // error 達到遞歸解除; ``` **4. 關于延遲綁定** ```php $result = 0; $one = function(){ var_dump($result); }; $two = function() use ($result){ var_dump($result); }; // 在回調生成的時候進行賦值; $four = function() use ($result){ //0 回調生成的時候賦值，也就是$result = 0; var_dump($result); }; // 如果使用引用,就能使use里面的變量完成延遲綁定,也就是在調用的時候再賦值; $three = function() use (&$result){ //1 在調用的時候再賦值進去，也就是1，注意對象類型也屬于引用； var_dump($result); }; $result += 1; $one(); // outputs NULL: $result is not in scope $two(); // outputs int(0): $result was copied $three(); // outputs int(1) $four(); // outputs int(0) ``` ## 幾個配合回調或閉包的函數 `bool array_walk ( array &$array , callable $funcname [, mixed $userdata = NULL ] )` ```php /** * @param array $array * @param callable $funcname () * @param mixed|NULL $userdata * @return bool * bool array_walk ( array &$array , callable $funcname [, mixed $userdata = NULL ] ) */ $fruits = array( "d" => "lemon" , "a" => "orange" , "b" => "banana" , "c" => "apple" ); $test_print = function(&$item2 , $key, $prefix){ $item2 .= ' 10'; echo "{$prefix} : $key => $item2\n"; }; /* this result : d => lemon this result : a => orange this result : b => banana this result : c => apple */ array_walk($fruits , $test_print, 'this result'); print_r($fruits); /* Array ( [d] => lemon 10 [a] => orange 10 [b] => banana 10 [c] => apple 10 ) */ ``` --- `bool array_walk_recursive ( array &$input , callable $funcname [, mixed $userdata = NULL ]` ```php $sweet = array( 'a' => 'apple' , 'b' => 'banana' ); $fruits = array( 'sweet' => $sweet , 'sour' => 'lemon' ); $test_print = function($item , $key) { echo "$key holds $item\n"; }; array_walk_recursive($fruits , $test_print); /* * 自動跳過sweet,因為sweet是數組;任何其值為 array 的鍵都不會被傳遞到回調函數中去 a holds apple b holds banana sour holds lemon */ ``` --- `array array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )` ```php $odd = function($var){ return ($var & 1); }; $even = function($var){ return (!($var & 1)); }; $array1 = array( "a" => 1 , "b" => 2 , "c" => 3 , "d" => 4 , "e" => 5 ); $array2 = array( 6 , 7 , 8 , 9 , 10 , 11 , 12 ); echo "Odd :\n"; print_r(array_filter($array1 , "odd")); /* Odd : Array ( [a] => 1 [c] => 3 [e] => 5 ) */ echo "Even:\n"; print_r(array_filter($array2 , "even")); /* Even: Array ( [0] => 6 [2] => 8 [4] => 10 [6] => 12 ) */ # 如果不傳第二參數的的話 $entry = array( 0 => 'foo', 1 => false, 2 => -1, 3 => null, 4 => '' ); print_r(array_filter($entry)); /* * 當前值為false的話就filter; Array ( [0] => foo [2] => -1 ) */ ``` --- `array array_map ( callable $callback , array $arr1 [, array $array ] )` ```php /** * @param callable $callback * @param array $arr1 * @param array $array */ $func = function($value) { return $value * 2; }; print_r(array_map($func, range(1, 5))); /* Array ( [0] => 2 [1] => 4 [2] => 6 [3] => 8 [4] => 10 ) */ $show_Spanish = function($n , $m){ return ("The number $n is called $m in Spanish"); }; $a = array( 1 , 2 , 3 , 4 , 5 ); $b = array( "uno" , "dos" , "tres" , "cuatro" , "cinco" ); $c = array_map($show_Spanish , $a , $b); /** print_r($c); Array ( [0] => The number 1 is called uno in Spanish [1] => The number 2 is called dos in Spanish [2] => The number 3 is called tres in Spanish [3] => The number 4 is called cuatro in Spanish [4] => The number 5 is called cinco in Spanish ) */ $map_Spanish = function($n , $m){ return (array($n => $m)); }; $d = array_map($map_Spanish , $a , $b); print_r($d); /** Array ( [0] => Array ( [1] => uno ) [1] => Array ( [2] => dos ) [2] => Array ( [3] => tres ) [3] => Array ( [4] => cuatro ) [4] => Array ( [5] => cinco ) ) */ ``` --- `mixed array_reduce ( array $input , callable $function [, mixed $initial = NULL ] )` ```php /** * 用回調函數迭代地將數組簡化為單一的結果值,解釋不清楚的一看代碼就明白了; * @param array $input * @param callable $function * @param mixed|NULL $initial 如果指定了可選參數 initial，該參數將被當成是數組中的第一個值來處理，或者如果數組為空的話就作為最終返回值。 */ $rsum = function($result , $value){ // $result 初始值為NULL, 如果有第三參數的話,第三參數為初始值; $result += $value; return $result; }; $rmul = function($result , $value){ $result *= $value; return $result; }; $a = array(1, 2, 3, 4, 5); $x = array(); $b = array_reduce($a, $rsum); // (NULL)0+1+2+3+4+5 = 15; $c = array_reduce($a, $rmul, 10); // 10*1*2*3*4*5 = 1200; $d = array_reduce($x, $rsum, "No data to reduce"); // No data to reduce ``` --- `mixed preg_replace_callback ( mixed $pattern , callable $callback , mixed $subject [, int $limit = -1 [, int &$count ]] )` ```php /** * @param mixed $pattern 正則模式; * @param callable $callback * @param mixed $subject * @param int $limit 對于每個模式用于每個 subject 字符串的最大可替換次數。 默認是-1（無限制）。 * @param int $count 如果指定，這個變量將被填充為替換執行的次數。 * mixed preg_replace_callback ( mixed $pattern , callable $callback , mixed $subject [, int $limit = -1 [, int &$count ]] ) */ // 將文本中的年份增加一年. $text = "April fools day is 04/01/2002\n"; $text .= "Last christmas was 12/24/2001\n"; // 回調函數 $next_year = function($matches){ // 通常: $matches[0]是完成的匹配 // $matches[1]是第一個捕獲子組的匹配 // 以此類推 return $matches[1] . ($matches[2] + 1); }; echo preg_replace_callback("|(\d{2}/\d{2}/)(\d{4})|" , $next_year , $text); ``` --- `mixed call_user_func ( callable $callback [, mixed $parameter [, mixed $... ]] )` `mixed call_user_func_array ( callable $callback , array $param_arr )` ```php /** * @param callable $callback 第一個參數為需要調用的函數; 如果是數組array($classname, $methodname) * @param mixed $parameter 第二個參數開始就是隊列進該函數的參數; * @param mixed $parameter2 * @param mixed $parameter3 * .. * @return 返回值：返回調用函數的結果，或FALSE */ $eat = function($fruit , $num){ //參數可以為多個 echo "You want to eat $fruit $num pcs, no problem\n"; }; call_user_func($eat , "apple" , 10); //print: You want to eat apple 10 pcs, no problem; call_user_func($eat , "orange" , 5); //print: You want to eat orange 5 pcs,no problem; // 調用類方法 class myclass { public static function say_hello($name,$message) { echo "Hello! $name $message"; } } //array(類名，靜態方法名),參數 call_user_func(array('myclass', 'say_hello'), 'dain_sun', 'good person'); call_user_func_array(array('myclass', 'say_hello'), array('dain_sun', 'good person')); // Hello! dain_sun good person ```