PHP array_filter帶參數

Question

我有以下代碼：

function lower_than_10($i) { 
    return ($i < 10); 
} 

，我可以用它來過濾像這樣的數組：

$arr = array(7, 8, 9, 10, 11, 12, 13); 
$new_arr = array_filter($arr, 'lower_than_10'); 

我如何添加參數lower_than_10以便它也可以接受要檢查的數字？喜歡，如果我有這個：

function lower_than($i, $num) { 
    return ($i < $num); 
} 

如何從array_filter調用它傳遞10到$ num或任何數字？

Answer 1

作爲替代@查爾斯的solution using closures，實際上你可以找到的文檔頁面上的例子in the comments。 的想法是，創建一個對象具有期望的狀態（$num）和回調方法（以$i作爲參數）：

class LowerThanFilter { 
     private $num; 

     function __construct($num) { 
       $this->num = $num; 
     } 

     function isLower($i) { 
       return $i < $this->num; 
     } 
} 

用法（demo）：

$arr = array(7, 8, 9, 10, 11, 12, 13); 
$matches = array_filter($arr, array(new LowerThanFilter(12), 'isLower')); 
print_r($matches); 

---

作爲旁註，您現在可以用更通用的NumericComparisonFilter替換LowerThanFilter，方法如isLower,isGreater,isEqual等只是一個想法—和demo ...

Answer 2

在PHP 5.3或更好的，你可以使用一個closure：

function create_lower_than($number = 10) { 
// The "use" here binds $number to the function at declare time. 
// This means that whenever $number appears inside the anonymous 
// function, it will have the value it had when the anonymous 
// function was declared. 
    return function($test) use($number) { return $test < $number; }; 
} 

// We created this with a ten by default. Let's test. 
$lt_10 = create_lower_than(); 
var_dump($lt_10(9)); // True 
var_dump($lt_10(10)); // False 
var_dump($lt_10(11)); // False 

// Let's try a specific value. 
$lt_15 = create_lower_than(15); 
var_dump($lt_15(13)); // True 
var_dump($lt_15(14)); // True 
var_dump($lt_15(15)); // False 
var_dump($lt_15(16)); // False 

// The creation of the less-than-15 hasn't disrupted our less-than-10: 
var_dump($lt_10(9)); // Still true 
var_dump($lt_10(10)); // Still false 
var_dump($lt_10(11)); // Still false 

// We can simply pass the anonymous function anywhere that a 
// 'callback' PHP type is expected, such as in array_filter: 
$arr = array(7, 8, 9, 10, 11, 12, 13); 
$new_arr = array_filter($arr, $lt_10); 
print_r($new_arr); 

Answer 3

在擴展jensgram答案您可以通過使用__invoke()魔術方法添加一些更神奇。

class LowerThanFilter { 
    private $num; 

    public function __construct($num) { 
     $this->num = $num; 
    } 

    public function isLower($i) { 
     return $i < $this->num; 
    } 

    function __invoke($i) { 
     return $this->isLower($i); 
    } 
} 

這將允許你這樣做

$arr = array(7, 8, 9, 10, 11, 12, 13); 
$matches = array_filter($arr, new LowerThanFilter(12)); 
print_r($matches); 

Answer 4

class ArraySearcher{ 

const OPERATOR_EQUALS = '=='; 
const OPERATOR_GREATERTHAN = '>'; 
const OPERATOR_LOWERTHAN = '<'; 
const OPERATOR_NOT = '!=';  

private $_field; 
private $_operation; 
private $_val; 

public function __construct($field,$operation,$num) { 
    $this->_field = $field; 
    $this->_operation = $operation; 
    $this->_val = $num; 
} 


function __invoke($i) { 
    switch($this->_operation){ 
     case '==': 
      return $i[$this->_field] == $this->_val; 
     break; 

     case '>': 
      return $i[$this->_field] > $this->_val; 
     break; 

     case '<': 
      return $i[$this->_field] < $this->_val; 
     break; 

     case '!=': 
      return $i[$this->_field] != $this->_val; 
     break; 
    } 
} 


} 

這使您可以在多維數組篩選項目：如果您在使用PHP 5.3及以上

$users = array(); 
$users[] = array('email' => 'user1@email.com','name' => 'Robert'); 
$users[] = array('email' => 'user2@email.com','name' => 'Carl'); 
$users[] = array('email' => 'user3@email.com','name' => 'Robert'); 

//Print all users called 'Robert' 
print_r(array_filter($users, new ArraySearcher('name',ArraySearcher::OPERATOR_EQUALS,'Robert'))); 

Answer 5

，你可以用closure來簡化你的代碼：

$NUM = 5; 
$items = array(1, 4, 5, 8, 0, 6); 
$filteredItems = array_filter($items, function($elem) use($NUM){ 
    return $elem < $NUM; 
}); 

Answer 6

如果需要多個參數傳遞給函數，你可以將它們添加到使用使用聲明「」：

$r = array_filter($anArray, function($anElement) use ($a, $b, $c){ 
    //function body where you may use $anElement, $a, $b and $c 
});