array_unshift

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

array_unshift — Añadir al inicio de un array uno a más elementos

Descripción

array_unshift(array &$array, mixed $... = ?): int

array_unshift() añade los elementos pasados al inicio de array. Observe que la lista de elementos se añade como un todo, por lo que los elementos añadidos permanecen en el mismo orden. Todas las claves numéricas del array serán modificadas empezando a contar desde cero mientras que las claves literales no serán cambiadas.

Parámetros

array: El array de entrada.
...: Los valores a añadir al inicio.

Valores devueltos

Devuelve el nuevo número de elementos del array.

Historial de cambios

Versión	Descripción
7.3.0	Esta función ahora puede ser llamada con un solo parámetro. Anteriormente, se requerían al menos dos parámetros.

Ejemplos

Ejemplo #1 Ejemplo de array_unshift()

<?php
$cola = array("naranja", "banana");
array_unshift($cola, "manzana", "frambuesa");
print_r($cola);
?>

El resultado del ejemplo sería:

Array
(
    [0] => manzana
    [1] => frambuesa
    [2] => naranja
    [3] => banana
)

Ver también

array_shift() - Quita un elemento del principio del array
array_push() - Inserta uno o más elementos al final de un array
array_pop() - Extrae el último elemento del final del array

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User Contributed Notes 13 notes

down

206

sergei at gmx dot net ¶

17 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'

);

down

rsmith_NOSPAM_ at _NOSPAM_unitec dot ac dot nz ¶

22 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.

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Anonymous ¶

12 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); 
} 
?>

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daniel at smallboxcms dot com ¶

9 years ago


Anonymous' associative version wasn't working for me, but it did with this small tweak:

function array_unshift_assoc(&$arr, $key, $val) 
{ 
    $arr = array_reverse($arr, true); 
    $arr[$key] = $val; 
    $arr = array_reverse($arr, true); 
    return $arr;
}

down

amschroeder at gmail dot com ¶

17 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...

down

php at electricsurfer dot com ¶

20 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;
}
?>

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robert dot wills at fuzzbrain dot uklinux dot net ¶

22 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

down

eliasritter168667 at gmail dot com ¶

11 months ago


This function helps if you want to prepend a key and value pair to the beginning of an array:

function array_kunshift(array $array, string|int $key, mixed $value): array {
        return array_merge([$key => $value], $array);
    }

down

Richard Akindele ¶

8 years ago


Another way to tack something to the beginning of an array is with array_merge().

$plans = array('AARP'=>'Senior', 'AAA'=>'Automobile Club');

$plans = array_merge(array("BAR"=>"Best Available Rate"),  $plans);

down

sahn at hmc dot edu ¶

23 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);

}

?>

down

-1

chris dot NoThxSpam dot given at hp dot com ¶

21 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);

}

?>

down

-4

John Brooking ¶

18 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 ));

?>

down

-12

lagroue ¶

20 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));

?>

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