array_unshift

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

array_unshift — Prepend one or more elements to the beginning of an array

Description

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

array_unshift() prepends passed elements to the front of the array. Note that the list of elements is prepended as a whole, so that the prepended elements stay in the same order. All numerical array keys will be modified to start counting from zero while literal keys won't be changed.

Note:
Resets array's internal pointer to the first element.

Parameters

array: The input array.
values: The values to prepend.

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_unshift() example

<?php
$queue = [
    "orange",
    "banana"
];

array_unshift($queue, "apple", "raspberry");
var_dump($queue);
?>

The above example will output:

array(4) {
  [0] =>
  string(5) "apple"
  [1] =>
  string(9) "raspberry"
  [2] =>
  string(6) "orange"
  [3] =>
  string(6) "banana"
}

Example #2 Usage with associative arrays

If one associative array is prepended to another associative array, the prepended array is numerically indexed into the former array.

<?php
$foods = [
    'apples' => [
        'McIntosh' => 'red',
        'Granny Smith' => 'green',
    ],
    'oranges' => [
        'Navel' => 'orange',
        'Valencia' => 'orange',
    ],
];
$vegetables = [
    'lettuce' => [
        'Iceberg' => 'green',
        'Butterhead' => 'green',
    ],
    'carrots' => [
        'Deep Purple Hybrid' => 'purple',
        'Imperator' => 'orange',
    ],
    'cucumber' => [
        'Kirby' => 'green',
        'Gherkin' => 'green',
    ],
];

array_unshift($foods, $vegetables);
var_dump($foods);

The above example will output:

array(3) {
  [0] =>
  array(3) {
    'lettuce' =>
    array(2) {
      'Iceberg' =>
      string(5) "green"
      'Butterhead' =>
      string(5) "green"
    }
    'carrots' =>
    array(2) {
      'Deep Purple Hybrid' =>
      string(6) "purple"
      'Imperator' =>
      string(6) "orange"
    }
    'cucumber' =>
    array(2) {
      'Kirby' =>
      string(5) "green"
      'Gherkin' =>
      string(5) "green"
    }
  }
  'apples' =>
  array(2) {
    'McIntosh' =>
    string(3) "red"
    'Granny Smith' =>
    string(5) "green"
  }
  'oranges' =>
  array(2) {
    'Navel' =>
    string(6) "orange"
    'Valencia' =>
    string(6) "orange"
  }
}

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User Contributed Notes 13 notes

down

211

sergei at gmx dot net ¶

16 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 ¶

21 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.

down

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); 
} 
?>

down

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;
}
?>

down

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 ¶

8 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

-1

chris dot NoThxSpam dot given at hp dot com ¶

20 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

-2

sahn at hmc dot edu ¶

22 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

-5

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

-11

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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array_unshift

Description

Parameters

Return Values

Changelog

Examples

See Also

Improve This Page

User Contributed Notes 13 notes