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    array_unshift

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

    array_unshift — Inserisce uno o più elementi all'inizio dell'array

    Descrizione

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

    array_unshift() aggiunge gli elementi specificati in testa ad array. Si noti che la lista di elementi è aggiunta in blocco, in modo tale che gli elementi rimangano nello stesso ordine. Tutte le chiavi numeriche vengono modificate per iniziare da zero mentre le chiavi alfabetiche non sono modificate.

    Restituisce il nuovo numero di elementi in array.

    Example #1 esempio di array_unshift()

    <?php
    $lista     = array("arancia", "banana");
    array_unshift($lista, "mela", "lampone");
    ?>

    In questo modo $lista conterrà i seguenti elementi: 

    Array
(
    [0] => mela
    [1] => lampone
    [2] => arancia
    [3] => banana
)

    Vedere anche array_shift(), array_push() e array_pop().

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    User Contributed Notes 13 notes

    up
    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'
    );
    up
    35
    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.
    up
    35
    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);
    }
    ?>
    up
    9
    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;
    }
    up
    2
    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...
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    2
    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;
    }
    ?>
    up
    2
    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
    up
    0
    eliasritter168667 at gmail dot com
    1 year 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);
        }
    up
    0
    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);
    up
    0
    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);
    }
    ?>
    up
    -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);
    }
    ?>
    up
    -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 ));
    ?>
    up
    -12
    lagroue
    21 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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