php教程

array_pad

(PHP 4, PHP 5, PHP 7)

array_pad — 以指定长度将一个值填充进数组

说明

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

array_pad() 返回 array 的一个拷贝，并用 value 将其填补到 size 指定的长度。如果 size 为正，则填补到数组的右侧，如果为负则从左侧开始填补。如果 size 的绝对值小于或等于 array 数组的长度则没有任何填补。有可能一次最多填补 1048576 个单元。

参数

array

需要被填充的原始数组。

size

新数组的长度。

value

将被填充的值，只有在 array 的现有长度小于 size 的长度时才有效。

返回值

返回 array 用 value 填充到 size 指定的长度之后的一个副本。 如果 size 为正，则填补到数组的右侧，如果为负则从左侧开始填补。 如果 size 的绝对值小于或等于 array 数组的长度则没有任何填补。

范例

Example #1 array_pad() 例子

<?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
?>

参见

  • array_fill() - 用给定的值填充数组
  • range() - 根据范围创建数组，包含指定的元素

User Contributed Notes

slava-san at mail dot ru 06-Jul-2013 10:58
// insert element to array
function array_insert(&$arr, $pos, $new_el=null) {
    $arraypad = array_pad($arr, count($arr)+1, 0);
    for ($i=count($arr)-1; $i>=$pos; $i--) {
        $arr[$i+1] = $arr[$i];
        if ($i == $pos) {
            $arr[$i] = $new_el;
        }
    }
}

$digits = array();
$digits[0] = 0;
$digits[1] = 1;
$digits[2] = 2;
$digits[3] = 3;
$digits[4] = 4;
$digits[5] = 5;
echo "was: "; var_dump($digits);

array_insert($digits, 3, 100);
echo "new: "; var_dump($digits);
sonu50imedbvu at gmail dot com(Sonu Jaiswal) 12-Jan-2011 12:53
Just an info about the value of "$pad_size" ,

If we set the value of "$pad_size" from -3 to 3,

It will produce the output like:

<?php
$result = array_pad($input, -3, "noop");
//result is array(12, 10, 9)

$result = array_pad($input, 3, "noop");
//result is array(12, 10, 9)
?>

means array will remain the same.
tugla 18-Dec-2008 09:23
Beware, if you try to pad an associative array using numeric keys, your keys will be re-numbered.

<?php
$a = array('size'=>'large', 'number'=>20, 'color'=>'red');
print_r($a);
print_r(array_pad($a, 5, 'foo'));

// use timestamps as keys
$b = array(1229600459=>'large', 1229604787=>20, 1229609459=>'red');
print_r($b);
print_r(array_pad($b, 5, 'foo'));
?>

yields this:
------------------
Array
(
    [size] => large
    [number] => 20
    [color] => red
)
Array
(
    [size] => large
    [number] => 20
    [color] => red
    [0] => foo
    [1] => foo
)
Array
(
    [1229600459] => large
    [1229604787] => 20
    [1229609459] => red
)
Array
(
    [0] => large
    [1] => 20
    [2] => red
    [3] => foo
    [4] => foo
)
hk, StrApp Bussiness Solutions 08-Jan-2007 02:15
A simple example for array_pad()

the syntax is as follows: array_pad(array(), (+/-)int, value)

where "array" is the array to which the value is to be added,

"(+/-) int" is a value that decides the length of the array(it should be greater than the length of the array.
if its a negative number then the value will be added at the left of the array else it will be added to the right.

"values" denotes the value to be added to the array

lets try an example:

<?php

$digits = array();
$digits[0] = 1;
$digits[1] = 2;
$digits[2] = 3;
$arraypad = array_pad($digits, -4, "0");
print_r($arraypad);

?>

output:

Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 )
oaev at mail dot ru 21-Oct-2004 11:48
Easy way to get an array contains 5 random numbers from 0 to 9:

$rand_arr = array_rand( array_pad( array(), 10, 1 ), 5 );
28-Feb-2004 09:00
One way to initialize a 20x20 multidimensional array. 

<?php
$a = array();
$b = array();
$b = array_pad($b,20,0);
$a = array_pad($a,20,$b);
?>
mwwaygoo at hotmail dot com 16-Jan-2004 08:02
little older, a little wiser.

ksort() will order the array back into its normal order again
so:

<?php
$myArr = array(2 => 'two', 4 => 'four');

$newArr = array_pad(array(), 6, 'FILLED');
$newArr =$myArr+$newArr;
ksort($newArr);
?>

Will give :
Array ( [0] => FILLED [1] => FILLED [2] => two [3] => FILLED [4] => four [5] => FILLED )
goffrie at sympatico dot ca 23-Mar-2003 05:06
To daarius - you mean you have...

[2]=>"two"
[3]=>"three"

and you want...

[0]=>"FILLED"
[1]=>"FILLED"
[2]=>"two"
[3]=>"three"
[4]=>"FILLED"
[5]=>"FILLED"

If so, then the following code...

<?php
$array = array(2 => "two", 3 => "three");
$array = array_pad($array, count($array)+2, "FILLED");
$num = -(count($array)+2);
$array = array_pad($array, $num, "FILLED");
print_r($array);
?>

will return:
Array ( [0] => FILLED [1] => FILLED [2] => two [3] => three [4] => FILLED [5] => FILLED )
The ordering should be okay,...
mwwaygoo at hotmail dot com 19-Sep-2002 09:39
OR you could do this

<?php
$myArr = array(2 => 'three', 3 => 'four');

$newArr = array_pad(array(), 4, 'FILLED');
$newArr =$myArr+$newArr;
?>

This gives your desired result BUT the ordering is a little wierd, because of the order they were added. Indexes are okay though and that is what you wanted.

print_r($newArr) outputs
Array ( [2] => three [3] => four [0] => FILLED [1] => FILLED )

hope this helps
daarius at hotmail dot com 23-Jul-2002 07:36
yes that is true. But, if the index of the array is 2=two, 3=three

and i want 4 more keys to be filled. But, not just filled anywhere, but i want to maintain the key index.

so, i would like to have 0=FILLED, 1=FILLED ... 4=FILLED, 5=FILLED

now i got 4 more keys padded with my string.

We can do this "if" we know the missing keys, but if we dont, then it would be nice for array_pad() or perhaps some new function to do this?

obviously we can achive this by looping through the array using array_key_exists(), and if you dont find the key, simply create + fill it.
regards,
Daarius...
scott*hurring.com 19-Jul-2002 04:20
to the previous commenter -- if you read the manual entry, you'd see that a negative pad_size will put the pad values at the front of the array.

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