带有参数的PHP array_filter

Question

我有以下代码:

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

我可以用来过滤这样的数组:

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

如何向lower_than_10添加参数,以便它还接受要检查的数字？就像,如果我有这个:

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

如何从array_filter调用它传递10到$ num或任何数字？

Answer 1

如果您使用的是php 5.3及更高版本,则可以使用闭包来简化代码:

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

Answer 2

作为使用闭包的 @ Charles 解决方案的替代方案,您实际上可以在文档页面的注释中找到一个示例.我们的想法是创建一个具有所需state($num)和回调方法($i作为参数)的对象:

class LowerThanFilter {
        private $num;

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

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

用法(演示):

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

作为一个旁注,你现在可以更换LowerThanFilter一个更通用的NumericComparisonFilter用类似的方法isLower,isGreater,isEqual等只是一个想法-和演示 ...

Answer 3

在PHP 5.3或更高版本中,您可以使用闭包:

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 4

如果需要将多个参数传递给函数,可以使用","将它们附加到use语句:

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

Answer 5

在jensgram答案的扩展中,您可以使用__invoke()魔术方法添加更多魔法.

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);
    }
}

这将允许你这样做

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

Answer 6

值得注意的是，自从 PHP 7.4箭头函数可用以来，这可以更简洁地完成：

$max = 10;
$arr = array(7, 8, 9, 10, 11, 12, 13);
$new_arr = array_filter($arr, fn ($n) => $n < $max);

Answer 7

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;
    }
}


}

这允许您过滤多维数组中的项目:

$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')) );