数组 函数
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array_pad

(PHP 4, PHP 5)

array_pad — 用值将数组填补到指定长度

说明

array array_pad ( array $input , int $pad_size , mixed $pad_value )

array_pad() 返回 input 的一个拷贝，并用 pad_value 将其填补到 pad_size 指定的长度。如果 pad_size 为正，则数组被填补到右侧，如果为负则从左侧开始填补。如果 pad_size 的绝对值小于或等于 input 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。

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() 和 range()。

数组 函数
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PHP手册 - N: 用值将数组填补到指定长度

用户评论:

sonu50imedbvu at gmail dot com(Sonu Jaiswal) (12-Jan-2011 08:53)

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 05:23)

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 10:15)

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 (22-Oct-2004 07:48)

Easy way to get an array contains 5 random numbers from 0 to 9:

$rand_arr = array_rand( array_pad( array(), 10, 1 ), 5 );

(29-Feb-2004 05:00)

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 04:02)

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 (24-Mar-2003 01:06)

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 05:39)

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 03:36)

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 (20-Jul-2002 12:20)

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.

ethanhunt314 at hotmail dot com (10-Dec-2000 12:25)

This is useful when using next() and prev() function in a while loop to traverse an array.

For example the following code will only output up to 8.

<?php
$test[] = "1";
$test[] = "2";
$test[] = "3";
$test[] = "4";
$test[] = "5";
$test[] = "6";
$test[] = "7";
$test[] = "8";
$test[] = "9";
$test[] = "10";
$test[] = " ";
$test[] = " ";
$test[] = " ";

$count = count($test);

while($i < $count) {

$now = current($test);
echo "<p>$now</p>";

next($test);
next($test);
next($test);
prev($test);
prev($test);
prev($test);


$i++;
next($test);
}
?>

But if you use:
$test = array_pad($test, 13, " ");

you will get all of your output.