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PHP / array_multisort — DevDocs

array_multisort

(PHP 4, PHP 5, PHP 7, PHP 8)

array_multisort Sort multiple or multi-dimensional arrays

Description

array_multisort(
 array &$array1,
 mixed $array1_sort_order = SORT_ASC,
 mixed $array1_sort_flags = SORT_REGULAR,
 mixed ...$rest
): bool

array_multisort() can be used to sort several arrays at once, or a multi-dimensional array by one or more dimensions.

Associative ( string ) keys will be maintained, but numeric keys will be re-indexed.

Note :

If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.

Note :

Resets array's internal pointer to the first element.

Parameters

array1

An array being sorted.

array1_sort_order

The order used to sort the previous array argument. Either SORT_ASC to sort ascendingly or SORT_DESC to sort descendingly.

This argument can be swapped with array1_sort_flags or omitted entirely, in which case SORT_ASC is assumed.

array1_sort_flags

Sort options for the previous array argument:

Sorting type flags:

  • SORT_REGULAR - compare items normally (don't change types)
  • SORT_NUMERIC - compare items numerically
  • SORT_STRING - compare items as strings
  • SORT_LOCALE_STRING - compare items as strings, based on the current locale. It uses the locale, which can be changed using setlocale()
  • SORT_NATURAL - compare items as strings using "natural ordering" like natsort()
  • SORT_FLAG_CASE - can be combined (bitwise OR) with SORT_STRING or SORT_NATURAL to sort strings case-insensitively

This argument can be swapped with array1_sort_order or omitted entirely, in which case SORT_REGULAR is assumed.

rest

More arrays, optionally followed by sort order and flags. Only elements corresponding to equivalent elements in previous arrays are compared. In other words, the sort is lexicographical.

Return Values

Returns true on success or false on failure.

Examples

Example #1 Sorting multiple arrays

<?php
$ar1 = array(10, 100, 100, 0);
$ar2 = array(1, 3, 2, 4);
array_multisort($ar1, $ar2);

var_dump($ar1);
var_dump($ar2);
?>

In this example, after sorting, the first array will contain 0, 10, 100, 100. The second array will contain 4, 1, 2, 3. The entries in the second array corresponding to the identical entries in the first array (100 and 100) were sorted as well.

array(4) {
  [0]=> int(0)
  [1]=> int(10)
  [2]=> int(100)
  [3]=> int(100)
}
array(4) {
  [0]=> int(4)
  [1]=> int(1)
  [2]=> int(2)
  [3]=> int(3)
}

Example #2 Sorting multi-dimensional array

<?php
$ar = array(
       array("10", 11, 100, 100, "a"),
       array(   1,  2, "2",   3,   1)
      );
array_multisort($ar[0], SORT_ASC, SORT_STRING,
                $ar[1], SORT_NUMERIC, SORT_DESC);
var_dump($ar);
?>

In this example, after sorting, the first array will transform to "10", 100, 100, 11, "a" (it was sorted as strings in ascending order). The second will contain 1, 3, "2", 2, 1 (sorted as numbers, in descending order).

array(2) {
  [0]=> array(5) {
    [0]=> string(2) "10"
    [1]=> int(100)
    [2]=> int(100)
    [3]=> int(11)
    [4]=> string(1) "a"
  }
  [1]=> array(5) {
    [0]=> int(1)
    [1]=> int(3)
    [2]=> string(1) "2"
    [3]=> int(2)
    [4]=> int(1)
  }
}

Example #3 Sorting database results

For this example, each element in the data array represents one row in a table. This type of dataset is typical of database records.

Example data:

volume | edition
-------+--------
    67 |       2
    86 |       1
    85 |       6
    98 |       2
    86 |       6
    67 |       7

The data as an array, called data . This would usually, for example, be obtained by looping with mysqli_fetch_assoc() .

<?php
$data[] = array('volume' => 67, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 1);
$data[] = array('volume' => 85, 'edition' => 6);
$data[] = array('volume' => 98, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 6);
$data[] = array('volume' => 67, 'edition' => 7);
?>

In this example, we will order by volume descending, edition ascending.

We have an array of rows, but array_multisort() requires an array of columns, so we use the below code to obtain the columns, then perform the sorting.

<?php
// Obtain a list of columns
foreach ($data as $key => $row) {
    $volume[$key]  = $row['volume'];
    $edition[$key] = $row['edition'];
}

// you can use array_column() instead of the above code
$volume  = array_column($data, 'volume');
$edition = array_column($data, 'edition');

// Sort the data with volume descending, edition ascending
// Add $data as the last parameter, to sort by the common key
array_multisort($volume, SORT_DESC, $edition, SORT_ASC, $data);
?>

The dataset is now sorted, and will look like this:

volume | edition
-------+--------
    98 |       2
    86 |       1
    86 |       6
    85 |       6
    67 |       2
    67 |       7

Example #4 Case insensitive sorting

Both SORT_STRING and SORT_REGULAR are case sensitive, strings starting with a capital letter will come before strings starting with a lowercase letter.

To perform a case insensitive sort, force the sorting order to be determined by a lowercase copy of the original array.

<?php
$array = array('Alpha', 'atomic', 'Beta', 'bank');
$array_lowercase = array_map('strtolower', $array);

array_multisort($array_lowercase, SORT_ASC, SORT_STRING, $array);

print_r($array);
?>

The above example will output:

Array
(
    [0] => Alpha
    [1] => atomic
    [2] => bank
    [3] => Beta
)

See Also

  • usort() - Sort an array by values using a user-defined comparison function
  • The comparison of array sorting functions
PHP / array_pad — DevDocs

array_pad

(PHP 4, PHP 5, PHP 7, PHP 8)

array_pad Pad array to the specified length with a value

Description

array_pad(array $array, int $length, mixed $value): array

array_pad() returns a copy of the array padded to size specified by length with value value . If length is positive then the array is padded on the right, if it's negative then on the left. If the absolute value of length is less than or equal to the length of the array then no padding takes place. It is possible to add at most 1048576 elements at a time.

Parameters

array

Initial array of values to pad.

length

New size of the array.

value

Value to pad if array is less than length .

Return Values

Returns a copy of the array padded to size specified by length with value value . If length is positive then the array is padded on the right, if it's negative then on the left. If the absolute value of length is less than or equal to the length of the array then no padding takes place.

Examples

Example #1 array_pad() example

<?php
$input = array(12, 10, 9);

$result = array_pad($input, 5, 0);
// result is array(12, 10, 9, 0, 0)

$result = array_pad($input, -7, -1);
// result is array(-1, -1, -1, -1, 12, 10, 9)

$result = array_pad($input, 2, "noop");
// not padded
?>

See Also

  • array_fill() - Fill an array with values
  • range() - Create an array containing a range of elements
Read article
PHP / array_pop — DevDocs

array_pop

(PHP 4, PHP 5, PHP 7, PHP 8)

array_pop Pop the element off the end of array

Description

array_pop(array &$array): mixed

array_pop() pops and returns the value of the last element of array , shortening the array by one element.

Note : This function will reset() the array pointer of the input array after use.

Parameters

array

The array to get the value from.

Return Values

Returns the value of the last element of array . If array is empty, null will be returned.

Examples

Example #1 array_pop() example

<?php
$stack = array("orange", "banana", "apple", "raspberry");
$fruit = array_pop($stack);
print_r($stack);
?>

After this, $stack will have only 3 elements:

Array
(
    [0] => orange
    [1] => banana
    [2] => apple
)

and raspberry will be assigned to $fruit .

See Also

  • array_push() - Push one or more elements onto the end of array
  • array_shift() - Shift an element off the beginning of array
  • array_unshift() - Prepend one or more elements to the beginning of an array
Read article
PHP / array_product — DevDocs

array_product

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

array_product Calculate the product of values in an array

Description

array_product(array $array): int|float

array_product() returns the product of values in an array.

Parameters

array

The array.

Return Values

Returns the product as an integer or float.

Examples

Example #1 array_product() examples

<?php

$a = array(2, 4, 6, 8);
echo "product(a) = " . array_product($a) . "\n";
echo "product(array()) = " . array_product(array()) . "\n";

?>

The above example will output:

product(a) = 384
product(array()) = 1
Read article
PHP / array_push — DevDocs

array_push

(PHP 4, PHP 5, PHP 7, PHP 8)

array_push Push one or more elements onto the end of array

Description

array_push(array &$array, mixed ...$values): int

array_push() treats array as a stack, and pushes the passed variables onto the end of array . The length of array increases by the number of variables pushed. Has the same effect as:

<?php
$array[] = $var;
?>
repeated for each passed value.

Note : If you use array_push() to add one element to the array, it's better to use $array[] = because in that way there is no overhead of calling a function.

Note : array_push() will raise a warning if the first argument is not an array. This differed from the $var[] behaviour where a new array was created, prior to PHP 7.1.0.

Parameters

array

The input array.

values

The values to push onto the end of the array .

Return Values

Returns the new number of elements in the array.

Changelog

Version Description
7.3.0 This function can now be called with only one parameter. Formerly, at least two parameters have been required.

Examples

Example #1 array_push() example

<?php
$stack = array("orange", "banana");
array_push($stack, "apple", "raspberry");
print_r($stack);
?>

The above example will output:

Array
(
    [0] => orange
    [1] => banana
    [2] => apple
    [3] => raspberry
)

See Also

  • array_pop() - Pop the element off the end of array
  • array_shift() - Shift an element off the beginning of array
  • array_unshift() - Prepend one or more elements to the beginning of an array
Read article
PHP / array_rand — DevDocs

array_rand

(PHP 4, PHP 5, PHP 7, PHP 8)

array_rand Pick one or more random keys out of an array

Description

array_rand(array $array, int $num = 1): int|string|array

Picks one or more random entries out of an array, and returns the key (or keys) of the random entries.

Caution

This function does not generate cryptographically secure values, and must not be used for cryptographic purposes, or purposes that require returned values to be unguessable.

If cryptographically secure randomness is required, the Random\Randomizer may be used with the Random\Engine\Secure engine. For simple use cases, the random_int() and random_bytes() functions provide a convenient and secure API that is backed by the operating system’s CSPRNG .

Parameters

array

The input array.

num

Specifies how many entries should be picked.

Return Values

When picking only one entry, array_rand() returns the key for a random entry. Otherwise, an array of keys for the random entries is returned. This is done so that random keys can be picked from the array as well as random values. If multiple keys are returned, they will be returned in the order they were present in the original array. Trying to pick more elements than there are in the array will result in an E_WARNING level error, and NULL will be returned.

Changelog

Version Description
7.1.0 The internal randomization algorithm has been changed to use the » Mersenne Twister Random Number Generator instead of the libc rand function.

Examples

Example #1 array_rand() example

<?php
$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$rand_keys = array_rand($input, 2);
echo $input[$rand_keys[0]] . "\n";
echo $input[$rand_keys[1]] . "\n";
?>

See Also

  • Random\Randomizer::pickArrayKeys() - Select random array keys
  • Random\Randomizer::shuffleArray() - Get a permutation of an array
Read article