array_filter
Обходит каждое значение массива array , передавая его в callback -функцию. Если callback -функция возвращает true , данное значение из array возвращается в результирующий array .
Ключи массива сохраняются и могут привести к пропускам, если array был проиндексирован. Результат массива ( array ) можно переиндексировать с помощью функции array_values() .
Список параметров
Если callback -функция не передана, все пустые значения массива array будут удалены. Смотрите empty() , чтобы узнать, как PHP определяет пустое значение в этом случае.
- ARRAY_FILTER_USE_KEY — передавать только ключ массива как аргумент для callback вместо значения
- ARRAY_FILTER_USE_BOTH — передавать и ключ, и значение в callback вместо только значения
Возвращаемые значения
Возвращает отфильтрованный массив.
Список изменений
| Версия | Описание |
|---|---|
| 8.0.0 | callback теперь допускает значение null. |
| 8.0.0 | Если параметр callback ожидает, что будет передано значение по ссылке, функция теперь выдаст ошибку уровня E_WARNING . |
Примеры
Пример #1 Пример использования array_filter()
<?php
function odd ( $var )
<
// является ли переданное число нечётным
return $var & 1 ;
>
function even ( $var )
<
// является ли переданное число чётным
return !( $var & 1 );
>
$array1 = [ ‘a’ => 1 , ‘b’ => 2 , ‘c’ => 3 , ‘d’ => 4 , ‘e’ => 5 ];
$array2 = [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ];
echo «Нечётные:\n» ;
print_r ( array_filter ( $array1 , «odd» ));
echo «Чётные:\n» ;
print_r ( array_filter ( $array2 , «even» ));
?>
Результат выполнения данного примера:
Пример #2 Использование array_filter() без callback -функции
print_r ( array_filter ( $entry ));
?>
Результат выполнения данного примера:
Пример #3 array_filter() с указанным mode
$arr = [ ‘a’ => 1 , ‘b’ => 2 , ‘c’ => 3 , ‘d’ => 4 ];
var_dump ( array_filter ( $arr , function( $k ) <
return $k == ‘b’ ;
>, ARRAY_FILTER_USE_KEY ));
var_dump ( array_filter ( $arr , function( $v , $k ) <
return $k == ‘b’ || $v == 4 ;
>, ARRAY_FILTER_USE_BOTH ));
?>
Результат выполнения данного примера:
Примечания
Если callback-функция изменяет массив (например, добавляет или удаляет элементы), поведение этой функции неопределённо.
Смотрите также
- array_intersect() — Вычисляет схождение массивов
- array_map() — Применяет callback-функцию ко всем элементам указанных массивов
- array_reduce() — Итеративно уменьшает массив к единственному значению, используя callback-функцию
- array_walk() — Применяет заданную пользователем функцию к каждому элементу массива
User Contributed Notes 8 notes
If you want a quick way to remove NULL, FALSE and Empty Strings («»), but leave values of 0 (zero), you can use the standard php function strlen as the callback function:
eg:
<?php
// removes all NULL, FALSE and Empty Strings but leaves 0 (zero) values
$result = array_filter ( $array , ‘strlen’ );
Note that a filtered array no longer encodes to json arrays, as the indices are no longer continuous:
$a = [‘a’, ‘b’, ‘c’];
var_dump(json_encode($a)); // [«a»,»b»,»c»]
$a = array_filter($a, function ($x) < return $x == 'b'; >);
var_dump(json_encode($a)); //
you can use array_values get a continuous array
If you like me have some trouble understanding example #1 due to the bitwise operator (&) used, here is an explanation.
The part in question is this callback function:
<?php
function odd ( $var )
<
// returns whether the input integer is odd
return( $var & 1 );
>
?>
If given an integer this function returns the integer 1 if $var is odd and the integer 0 if $var is even.
The single ampersand, &, is the bitwise AND operator. The way it works is that it takes the binary representation of the two arguments and compare them bit for bit using AND. If $var = 45, then since 45 in binary is 101101 the operation looks like this:
45 in binary: 101101
1 in binary: 000001
——
result: 000001
Only if the last bit in the binary representation of $var is changed to zero (meaning that the value is even) will the result change to 000000, which is the representation of zero.
Keep in mind that, as of PHP 7.4 and above, you can use arrow functions to as argument.
So for example if you want to leave values bigger than 10:
<?php
$arr = array_filter ( $numbers , fn ( $n ) => $n > 10 );
?>
also, combine with key-flag to cut certain keys:
<?php
$arr = array_filter ( $entries , fn ( $key ) => ! in_array ( $key , [ ‘key1’ , ‘key5’ ]), ARRAY_FILTER_USE_KEY );
?>
and so on.
Some of PHP’s array functions play a prominent role in so called functional programming languages, where they show up under a slightly different name:
<?php
array_filter () -> filter (),
array_map () -> map (),
array_reduce () -> foldl () ( «fold left» )
?>
Functional programming is a paradigm which centers around the side-effect free evaluation of functions. A program execution is a call of a function, which in turn might be defined by many other functions. One idea is to use functions to create special purpose functions from other functions.
The array functions mentioned above allow you compose new functions on arrays.
E.g. array_sum = array_map(«sum», $arr).
This leads to a style of programming that looks much like algebra, e.g. the Bird/Meertens formalism.
E.g. a mathematician might state
map(f o g) = map(f) o map(g)
the so called «loop fusion» law.
Many functions on arrays can be created by the use of the foldr() function (which works like foldl, but eating up array elements from the right).
I can’t get into detail here, I just wanted to provide a hint about where this stuff also shows up and the theory behind it.
Depending on the intended meanings of your «empty» array values, e.g., null and empty string, vs. an integer 0 or a boolean false, be mindful of the result of different filters.
<?php
declare( strict_types = 1 );
$array = array( ‘null’ => null , ‘nullstring’ => » , ‘intzero’ => 0 , ‘stringzero’ => ‘0’ , ‘false’ => false , ‘stringfalse’ => ‘false’ , );
// Removes null, null-string — but also FALSE!
$filtered1 = array_filter ( $array , ‘strlen’ );
// Removes only null.
$filtered2 = array_filter ( $array , function( $v ) < return ! is_null ( $v ); >);
// Removes null and null-string. Keeps FALSE and 0.
$filtered3 = array_filter ( $array , function( $v ) < return !( is_null ( $v ) or '' === $v ); >);
var_dump ( $array , $filtered1 , $filtered2 , $filtered3 );
?>
Results in:
array (size=3)
‘intzero’ => int 0
‘stringzero’ => string ‘0’ (length=1)
‘stringfalse’ => string ‘false’ (length=5)
array (size=5)
‘nullstring’ => string » (length=0)
‘intzero’ => int 0
‘stringzero’ => string ‘0’ (length=1)
‘false’ => boolean false
‘stringfalse’ => string ‘false’ (length=5)
array (size=4)
‘intzero’ => int 0
‘stringzero’ => string ‘0’ (length=1)
‘false’ => boolean false
‘stringfalse’ => string ‘false’ (length=5)
My favourite use of this function is converting a string to an array, trimming each line and removing empty lines:
<?php
$array = array_filter ( array_map ( ‘trim’ , explode ( «\n» , $string )), ‘strlen’ );
?>
Although it states clearly that array keys are preserved, it’s important to note this includes numerically indexed arrays. You can’t use a for loop on $array above without processing it through array_values() first.
Check if all elements in array are not empty/null/falsy.
——————————
Supposing you have a one dimensional array.
<?php
$spicy_numbers = [ 69 , 420 , ɸ ];
?>
And you want to easily check that all elements in said array are not null/empty/any falsy value, instead of running a loop over each element, you can pass the array to <?php array_filter () ?> , with no callback function, and then check if the returned array is the same size as the original, since <?php array_filter () ?> strips out all non-truthy values including 0 when no callback is provided.
Example:
<?php
$spicy_numbers = [ 69 , 420 , » ]; // Phi is gone!
if ( count ( array_filter ( $spicy_numbers ) ) !== count ( $spicy_numbers ) ) <
// One of the elements is empty/null/falsy.
> else <
// All elements present and truthy.
>
?>
As a neat little function, you could do this:
<?php
/**
* Checks if all of given array’s elements have a non-falsy value.
* Use-case: If all items in array are set and have a value (truthy, of course), then do X; else, do Y.
*
* @param array $arr
* @return bool
*/
function is_array_full ( $arr ) <
$array_count = count ( $arr );
$filtered_count = count ( array_filter ( $arr ) );
return ( $array_count === $filtered_count ) ? true : false ;
>
?>
How to Remove Empty Array Elements in PHP
Frequently, some elements in an array can be empty, and it is necessary to remove them. In this short tutorial, we will provide you with the right function to do that.
The most common and correct way is to use the array_filter function. It will remove any element that is evaluated as FALSE (null, false, », 0). By adding a callback function, you can customize the filter.
Here is how the array_filter works:
In the example above, the value of $array is what is demonstrated below it in the brackets.
That operates properly but may leave index gaps inside an array. Luckily, you can fix it with the help of array_values for re-indexing the array like this:
In this example, as well, the value of $array is what is demonstrated below it in the brackets.
Describing the array_filter Function
This function is capable of iterating over every value in the array and pass them to the callback function.
Once the callback function returns True, the current value from the array gets back into the result array.
The array_filter function has the following parameters: array, callback, and flag.
The first one is the array to iterate over. Callback is the callback function to apply. And, the flag specifies what arguments are forwarded to the callback.
Php как удалить пустые элементы массива
Сколько функций умеют удалять пустые ячейки массива? Вот эти функции вспомнил, которыми сам пользуюсь для удаления пустых ячеек массива!
Функция для удаления пустых ячеек массива в php — array_diff :
Функция для удаления пустых ячеек массива в php — array_delete, с использованием предыдущей функции, но с восстановлением нумерации ключей :
Функция для удаления пустых ячеек массива в php — array_filter :
Пример удаления пустых ячеек массива
Для иллюстрации удаления пустой/пустых ячеек массива в php нам потребуется тестовый массив :
Remove Empty Array Elements in PHP
In this article, we will introduce methods to remove the empty array elements in PHP.
- Using array_filter() function
- Using array_diff() function
- Using unset() function
Use array_filter() Function to Remove the Empty Array Elements in PHP
Please enable JavaScript
The built-in function array_filter() removes all the empty elements, zeros, false and null values from an array. This function uses a callback function to filter the array values. If no callback function is specified, it removes the empty elements, zeros, false and null values.
The correct syntax to use this function is as follows
Here the $arrayName is the only mandatory parameter. The parameter $callbackFunction is the callback function specified for the operation on the array. The parameter $callbackParameter tells about the parameters passed to the callback function.
We have not specified any callback function, hence the returned array has no empty elements, zeros, and null values.
Use array_diff() Function to Remove the Empty Array Elements in PHP
The built-in function array_diff() is used to find the difference between two or more arrays . It can be used to delete empty elements from an array. It does not re-index the array. The correct syntax to use this function is as follows.
It takes N number of the parameters (arrays). It compares the first array with all other arrays. It returns an array that contains all the elements of the first array that are not present in other arrays.
Here, we have compared our array with an array that contains the empty string, 0, and null value. Then the returned array has no empty elements.
Use unset() Function to Remove the Empty Array Elements in PHP
The unset() function removes the value stored in a variable. We can use it to remove the empty elements from an array. The correct syntax to use this function is as follows.
It only accepts one parameter $variableName . The $variableName is a variable of which we want to remove the value.
Here, we have used a foreach loop to find the empty array elements. If an array element is empty, its index along with array name is passed as a parameter to the unset() function.