array_unshift

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John Brooking
03-Jun-2006 09:54


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:



   array_unshift( $myArray, array_shift( $myArray ));

07-Nov-2005 03:38


function multi_array_search($search_value, $the_array)

{

   if (is_array($the_array))

   {

       foreach ($the_array as $key => $value)

       {

           $result = multi_array_search($search_value, $value);

           if (is_array($result))

           {

               $return = $result;

               array_unshift($return, $key);

               return $return;

           }

           elseif ($result == true)

           {

               $return[] = $key;

               return $return;

           }

       }

       return false;

   }

   else

   {

       if ($search_value == $the_array)

       {

           return true;

       }

       else return false;

   }

}

php at electricsurfer dot com
27-Feb-2004 10:20


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;

}

?>

lagroue
09-Nov-2003 08:46


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));


?>

chris dot NoThxSpam dot given at hp dot com
24-Jul-2003 03:17


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);


}


?>

rsmith_NOSPAM_ at _NOSPAM_unitec dot ac dot nz
31-Jul-2002 10:00


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.

TimHyde at C21Technology dot com
18-Jul-2002 08:04


A simpler way to implement an array_unshift with key=>value pairs (i.e. similar to the example using array_reverse above) is to use array_merge.  i.e.





<?php


$arrayone=array_merge(array("newkey"=>"newvalue"),$arrayone);


?>





Obviously you need to take care when adding numeric or duplicate keys.

jrh_at_geodata.soton.ac.uk
11-Jul-2002 12:30


I have found array_unshift is a function that should be avoided when unshifting lots of data in large arrays.



In a recent script I wrote, it took approx. 24 seconds to unshift 3500 timestamps to an array, a work around could be to use array_reverse and array_push. Array_push is much faster due to the indexing.

robert dot wills at fuzzbrain dot uklinux dot net
07-Feb-2002 10:02


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

sahn at hmc dot edu
28-Jul-2001 03:21


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);


}


?>

matt at synergie dot net
19-Sep-2000 01:20


The behaviour of unshift nearly caught me out.


Not only is the item added at the start of the list but the list is re-indexed too.





<?php





$a = array(5=>"five", 6 =>"six", 20 => "twenty");





while(list($key, $value) = each($a)) 


    echo "k: $key v: $value<BR>\n";





echo "<BR>\n";


array_unshift($a, "zero");








while(list($key, $value) = each($a)) 


    echo "k: $key v: $value<BR>\n";





?>





k: 5 v: five


k: 6 v: six


k: 20 v: twenty





k: 0 v: zero


k: 1 v: five


k: 2 v: six


k: 3 v: twenty

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