PHP 5.4.36 Released

array_unshift

(PHP 4, PHP 5)

array_unshiftДобавляет один или несколько элементов в начало массива

Описание

int array_unshift ( array &$array , mixed $var [, mixed $... ] )

array_unshift() добавляет переданные в качестве аргументов элементы в начало массива array. Обратите внимание, что список элементов добавляется целиком, то есть порядок элементов сохраняется. Все числовые ключи будут изменены таким образом, что нумерация массива будет начинаться с нуля, в то время как строковые ключи останутся прежними.

Список параметров

array

Входной массив.

var

Добавляемая в начало переменная.

Возвращаемые значения

Возвращает новое количество элементов в array.

Примеры

Пример #1 Пример использования array_unshift()

<?php
$queue 
= array("orange""banana");
array_unshift($queue"apple""raspberry");
print_r($queue);
?>

Результат выполнения данного примера:

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

Смотрите также

  • array_shift() - Извлекает первый элемент массива
  • array_push() - Добавляет один или несколько элеметов в конец массива
  • array_pop() - Извлекает последний элемент массива

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User Contributed Notes 10 notes

up
25
Anonymous
3 years ago
Sahn's example almost works but has a small error. Try it like this if you need to prepend something to the array without the keys being reindexed and/or need to prepend a key value pair, you can use this short function:

<?php
function array_unshift_assoc(&$arr, $key, $val)
{
   
$arr = array_reverse($arr, true);
   
$arr[$key] = $val;
    return =
array_reverse($arr, true);
}
?>
up
23
sergei at gmx dot net
7 years ago
You can preserve keys and unshift an array with numerical indexes in a really simple way if you'll do the following:

<?php
$someArray
=array(224=>'someword1', 228=>'someword2', 102=>'someword3', 544=>'someword3',95=>'someword4');

$someArray=array(100=>'Test Element 1 ',255=>'Test Element 2')+$someArray;
?>

now the array looks as follows:

array(
100=>'Test Element 1 ',
255=>'Test Element 2'
224=>'someword1',
228=>'someword2',
102=>'someword3',
544=>'someword3',
95=>'someword4'
);
up
7
rsmith_NOSPAM_ at _NOSPAM_unitec dot ac dot nz
12 years ago
array_merge() will also reindex (see array_merge() manual entry), but the '+' operator won't, so...

<?php
$arrayone
=array("newkey"=>"newvalue") + $arrayone;
?>

does the job.
up
4
robert dot wills at fuzzbrain dot uklinux dot net
12 years ago
Actually this problem with the keys getting reindexed only happens when the keys are numerical:

<?php

$a
= array("f"=>"five", "s" =>"six", "t" =>
       
"twenty");

print_r($a);
echo
"\n";
foreach(
$a as $key=>$val)
{
    echo
"k: $key v: $val \n";
}

array_unshift($a, "zero");
print_r($a);
echo
"\n";
foreach(
$a as $key=>$val)
{
    echo
"k: $key v: $val \n";
}
?>

Array
(
    [f] => five
    [s] => six
    [t] => twenty
)

k: f v: five
k: s v: six
k: t v: twenty
Array
(
    [0] => zero
    [f] => five
    [s] => six
    [t] => twenty
)

k: 0 v: zero
k: f v: five
k: s v: six
k: t v: twenty
up
3
amschroeder at gmail dot com
7 years ago
This becomes a nice little problem if you index your arrays out of order (while manually sorting).  For example:

<?php
$recordMonths
[3] = '8/%/2006';
$recordMonths[4] = '7/%/2004';
$recordMonths[0] = '3/%/2007';
$recordMonths[1] = '2/%/2007';
$recordMonths[5] = '12/%/2000';
$recordMonths[6] = '11/%/2000';
$recordMonths[7] = '10/%/2000';
$recordMonths[2] = '1/%/2007';

for(
$i = 0; $i < count($recordMonths); $i++)
{
   
$singleMonth = $recordMonths[$i];
    echo
"singleMonth: $singleMonth <br />";
}
array_unshift($recordMonths,'%');
for(
$i = 0; $i < count($recordMonths); $i++)
{
   
$singleMonth = $recordMonths[$i];
    echo
"singleMonth: $singleMonth <br />";
}
?>

Produces:

singleMonth: 3/%/2007
singleMonth: 2/%/2007
singleMonth: 1/%/2007
singleMonth: 8/%/2006
singleMonth: 7/%/2004
singleMonth: 12/%/2000
singleMonth: 11/%/2000
singleMonth: 10/%/2000
singleMonth: %
singleMonth: 8/%/2006
singleMonth: 7/%/2004
singleMonth: 3/%/2007
singleMonth: 2/%/2007
singleMonth: 12/%/2000
singleMonth: 11/%/2000
singleMonth: 10/%/2000
singleMonth: 1/%/2007

It reindexes them based on the order they were created.  It seems like if an array has all numeric indexes, then it should reindex them based on the order of their index.  Just my opinion...
up
1
sahn at hmc dot edu
13 years ago
If you need to prepend something to the array without the keys being reindexed and/or need to prepend a key value pair, you can use this short function:

<?php
function array_unshift_assoc(&$arr, $key, $val)
{
   
$arr = array_reverse($arr, true);
   
$arr[$key] = $val;
   
$arr = array_reverse($arr, true);
    return
count($arr);
}
?>
up
0
John Brooking
8 years ago
I had a need tonight to convert a numeric array from 1-based to 0-based, and found that the following worked just fine due to the "side effect" of renumbering:

<?php
   array_unshift
( $myArray, array_shift( $myArray ));
?>
up
0
php at electricsurfer dot com
10 years ago
even simpler unshifting of a reference !
<?php
/**
* @return int
* @param $array array
* @param $value mixed
* @desc Prepend a reference to an element to the beginning of an array. Renumbers numeric keys, so $value is always inserted to $array[0]
*/
function array_unshift_ref(&$array, &$value)
{
  
$return = array_unshift($array,'');
  
$array[0] =& $value;
   return
$return;
}
?>
up
0
lagroue
11 years ago
Last version of PHP deprecated unshifting of a reference.
You can use this function instead :

<?php
function array_unshift1 (& $ioArray, $iValueWrappedInAnArray) {
   
$lNewArray = false;
    foreach (
array_keys ($ioArray) as $lKey)
       
$lNewArray[$lKey+1] = & $ioArray[$lKey];
   
$ioArray = array (& $iValueWrappedInAnArray[0]);
    if (
$lNewArray)
        foreach (
array_keys ($lNewArray) as $lKey)
            
$ioArray[] = & $lNewArray[$lKey];
    return
count($ioArray);
}

// before last PHP (now generates a deprecation warning)
array_unshift ($a, &$v);
// since last PHP (caution, there is a wrapping array !!)
array_unshift1 ($a, array (&$v));
?>
up
0
chris dot NoThxSpam dot given at hp dot com
11 years ago
If you need to change the name of a key without changing its position in the array this function may be useful.

<?php
function array_key_change($Old, $New, $In, $NewVal=NULL) {
       
$Temp = array();
        while(isset(
$Temp[$Old]) == false) {
                list(
$k, $v) = each($In);
               
$Temp[$k] = $v;
                unset(
$In[$k]);
        }
        if(
$NewVal == NULL) {
               
$NewVal = $Temp[$Old];
        }
        unset(
$Temp[$Old]);
       
$Temp = array_reverse($Temp);
       
$In = array_merge(array($New=>$NewVal), $In);
        while(list(
$k,$v) = each($Temp)) {
               
$In = array_merge(array($k=>$v), $In);
        }
        return(
$In);
}
?>
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