Arrays

  • Introduction
  • Installing/Configuring
  • Predefined Constants
  • Sorting Arrays
  • Array Functions
    • array_change_key_case — Changes the case of all keys in an array
    • array_chunk — Split an array into chunks
    • array_column — Return the values from a single column in the input array
    • array_combine — Creates an array by using one array for keys and another for its values
    • array_count_values — Counts the occurrences of each distinct value in an array
    • array_diff_assoc — Computes the difference of arrays with additional index check
    • array_diff_key — Computes the difference of arrays using keys for comparison
    • array_diff_uassoc — Computes the difference of arrays with additional index check which is performed by a user supplied callback function
    • array_diff_ukey — Computes the difference of arrays using a callback function on the keys for comparison
    • array_diff — Computes the difference of arrays
    • array_fill_keys — Fill an array with values, specifying keys
    • array_fill — Fill an array with values
    • array_filter — Filters elements of an array using a callback function
    • array_flip — Exchanges all keys with their associated values in an array
    • array_intersect_assoc — Computes the intersection of arrays with additional index check
    • array_intersect_key — Computes the intersection of arrays using keys for comparison
    • array_intersect_uassoc — Computes the intersection of arrays with additional index check, compares indexes by a callback function
    • array_intersect_ukey — Computes the intersection of arrays using a callback function on the keys for comparison
    • array_intersect — Computes the intersection of arrays
    • array_is_list — Checks whether a given array is a list
    • array_key_exists — Checks if the given key or index exists in the array
    • array_key_first — Gets the first key of an array
    • array_key_last — Gets the last key of an array
    • array_keys — Return all the keys or a subset of the keys of an array
    • array_map — Applies the callback to the elements of the given arrays
    • array_merge_recursive — Merge one or more arrays recursively
    • array_merge — Merge one or more arrays
    • array_multisort — Sort multiple or multi-dimensional arrays
    • array_pad — Pad array to the specified length with a value
    • array_pop — Pop the element off the end of array
    • array_product — Calculate the product of values in an array
    • array_push — Push one or more elements onto the end of array
    • array_rand — Pick one or more random keys out of an array
    • array_reduce — Iteratively reduce the array to a single value using a callback function
    • array_replace_recursive — Replaces elements from passed arrays into the first array recursively
    • array_replace — Replaces elements from passed arrays into the first array
    • array_reverse — Return an array with elements in reverse order
    • array_search — Searches the array for a given value and returns the first corresponding key if successful
    • array_shift — Shift an element off the beginning of array
    • array_slice — Extract a slice of the array
    • array_splice — Remove a portion of the array and replace it with something else
    • array_sum — Calculate the sum of values in an array
    • array_udiff_assoc — Computes the difference of arrays with additional index check, compares data by a callback function
    • array_udiff_uassoc — Computes the difference of arrays with additional index check, compares data and indexes by a callback function
    • array_udiff — Computes the difference of arrays by using a callback function for data comparison
    • array_uintersect_assoc — Computes the intersection of arrays with additional index check, compares data by a callback function
    • array_uintersect_uassoc — Computes the intersection of arrays with additional index check, compares data and indexes by separate callback functions
    • array_uintersect — Computes the intersection of arrays, compares data by a callback function
    • array_unique — Removes duplicate values from an array
    • array_unshift — Prepend one or more elements to the beginning of an array
    • array_values — Return all the values of an array
    • array_walk_recursive — Apply a user function recursively to every member of an array
    • array_walk — Apply a user supplied function to every member of an array
    • array — Create an array
    • arsort — Sort an array in descending order and maintain index association
    • asort — Sort an array in ascending order and maintain index association
    • compact — Create array containing variables and their values
    • count — Counts all elements in an array or in a Countable object
    • current — Return the current element in an array
    • each — Return the current key and value pair from an array and advance the array cursor
    • end — Set the internal pointer of an array to its last element
    • extract — Import variables into the current symbol table from an array
    • in_array — Checks if a value exists in an array
    • key_exists — Alias of array_key_exists
    • key — Fetch a key from an array
    • krsort — Sort an array by key in descending order
    • ksort — Sort an array by key in ascending order
    • list — Assign variables as if they were an array
    • natcasesort — Sort an array using a case insensitive "natural order" algorithm
    • natsort — Sort an array using a "natural order" algorithm
    • next — Advance the internal pointer of an array
    • pos — Alias of current
    • prev — Rewind the internal array pointer
    • range — Create an array containing a range of elements
    • reset — Set the internal pointer of an array to its first element
    • rsort — Sort an array in descending order
    • shuffle — Shuffle an array
    • sizeof — Alias of count
    • sort — Sort an array in ascending order
    • uasort — Sort an array with a user-defined comparison function and maintain index association
    • uksort — Sort an array by keys using a user-defined comparison function
    • usort — Sort an array by values using a user-defined comparison function
add a note add a note

User Contributed Notes 17 notes

up
90
applegrew at rediffmail dot com
16 years ago
For newbies like me.

Creating new arrays:-
//Creates a blank array.
$theVariable = array();

//Creates an array with elements.
$theVariable = array("A", "B", "C");

//Creating Associaive array.
$theVariable = array(1 => "http//google.com", 2=> "http://yahoo.com");

//Creating Associaive array with named keys
$theVariable = array("google" => "http//google.com", "yahoo"=> "http://yahoo.com");

Note:
New value can be added to the array as shown below.
$theVariable[] = "D";
$theVariable[] = "E";
up
15
Tyler Bannister
15 years ago
To delete an individual array element use the unset function

For example:

<?PHP
    $arr
= array( "A", "B", "C" );
    unset(
$arr[1] );
   
// now $arr = array( "A", "C" );
?>

Unlink is for deleting files.
up
0
justin at jmfrazier dot com
4 years ago
Using null as the key when setting an array value is NOT the same as using empty [].
<?php
  $null
= null;
 
$testArray = [];
 
$testArray[$null] = 1;
 
$testArray[$null] = 2;
 
$testArray[$null] = 3;
 
$testArray[$null] = 4;
 
var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray
= [];
 
$testArray[null] = 1;
 
$testArray[null] = 2;
 
$testArray[null] = 3;
 
$testArray[null] = 4;
 
var_dump($testArray);
?>
Output:
array(1) {
  '' =>
  int(4)
}

<?php
  $testArray
= [];
 
$testArray[] = 1;
 
$testArray[] = 2;
 
$testArray[] = 3;
 
$testArray[] = 4;
 
var_dump($testArray);
?>
Output:
array(4) {
  [0] =>
  int(1)
  [1] =>
  int(2)
  [2] =>
  int(3)
  [3] =>
  int(4)
}
up
-3
web at houhejie dot cn
6 years ago
string2array($str):

$arr=json_decode('["fileno",["uid","uname"],"topingid",["touid",[1,2,[3,4]],"touname"]]');
print_r($arr);

output:
Array ( [0] => fileno [1] => Array ( [0] => uid [1] => uname ) [2] => topingid [3] => Array ( [0] => touid [1] => Array ( [0] => 1 [1] => 2 [2] => Array ( [0] => 3 [1] => 4 ) ) [2] => touname ) )

when I hope a function string2array($str), "spam2"  suggest this. and It works well~~~hope this helps us,  and add to the Array function list
up
-5
info at curtinsNOSPAMcreations dot com
13 years ago
Another way to create a multidimensional array that looks a lot cleaner is to use json_decode.  (Note that this probably adds a touch of overhead, but it sure does look nicer.)  You can of course add as many levels and as much formatting as you'd like to the string you then decode.  Don't forget that json requires " around values, not '!!  (So, you can't enclose the json string with " and use ' inside the string.)

As an example:

<?php
    $myarray
['blah'] = json_decode('[
        {"label":"foo","name":"baz"},
        {"label":"boop","name":"beep"}
    ]'
,true);

print_r($myarray)
?>
returns:

Array
(
    [blah] => Array
        (
            [0] => Array
                (
                    [label] => foo
                    [name] => baz
                )

            [1] => Array
                (
                    [label] => boop
                    [name] => beep
                )
        )
)
up
-4
macnimble at gmail dot com
15 years ago
Converting a linear array (like a mysql record set) into a tree, or multi-dimensional array can be a real bugbear. Capitalizing on references in PHP, we can 'stack' an array in one pass, using one loop, like this:

<?php
# array_stack()
# Original idea from:
# http://www.ideashower.com/our_solutions/
#   create-a-parent-child-array-structure-in-one-pass/
function array_stack (&$a, $p = '@parent', $c = '@children')
{
 
$l = $t = array();
  foreach (
$a AS $key => $val):
    if (!
$val[$p]) $t[$key] =& $l[$key];
    else
$l[$val[$p]][$c][$key] =& $l[$key];
   
$l[$key] = (array)$l[$key] + $val;
  endforeach;
  return
$a = array('tree' => $t, 'leaf' => $l);
}

# Example:
$node = array();
$node[1] = array('@parent' => 0, 'title' => 'I am node 1.');
#     ^-----------------------v Link @parent value to key.
$node[2] = array('@parent' => 1, 'title' => 'I am node 2.');
$node[3] = array('@parent' => 2, 'title' => 'I am node 3.');
$node[4] = array('@parent' => 1, 'title' => 'I am node 4.');
$node[5] = array('@parent' => 4, 'title' => 'I am node 5.');

array_stack($node);

$node['leaf'][1]['title'] = 'I am node one.';
$node['leaf'][2]['title'] = 'I am node two.';
$node['leaf'][3]['title'] = 'I am node three.';
$node['leaf'][4]['title'] = 'I am node four.';
$node['leaf'][5]['title'] = 'I am node five.';

echo
'<pre>',print_r($node['tree'],TRUE),'</pre>';
?>

Note that there's no parameter checking on the array value, but this is only to keep the function size small. One could easily a quick check in there to make sure the $a parameter was in fact an array.

Hope you find it useful. Huge thanks to Nate Weiner of IdeaShower.com for providing the original function I built on.
up
-5
dragos dot rusu at NOSPAM dot bytex dot ro
14 years ago
If an array item is declared with key as NULL, array key will automatically be converted to empty string '', as follows:

<?php
$a
= array(
   
NULL => 'zero',
   
1    => 'one',
   
2    => 'two');

// This will show empty string for key associated with "zero" value
var_dump(array_keys($a));

// Array elements are shown
reset($a);
while(
key($a) !== NULL )
{
  echo
key($a) . ": ".current($a) . "<br>";// PHP_EOL
 
next($a);
}

// Array elements are not shown
reset($a);
while(
key($a) != NULL ) // '' == null   => no iteration will be executed
{
  echo
key($a) . ": ".current($a) . "<br>";// PHP_EOL
 
next($a);
}
up
-6
Anonymous
15 years ago
@jorge at andrade dot cl
This variant is faster:
<?php
function array_avg($array,$precision=2){
    if(!
is_array($array))
        return
'ERROR in function array_avg(): this is a not array';

    foreach(
$array as $value)
        if(!
is_numeric($value))
            return
'ERROR in function array_avg(): the array contains one or more non-numeric values';
   
   
$cuantos=count($array);
  return
round(array_sum($array)/$cuantos,$precision);
}
?>
up
-5
andyd273 at gmail dot com
15 years ago
A small correction to Endel Dreyer's PHP array to javascript array function. I just changed it to show keys correctly:

            function array2js($array,$show_keys)
            {
                $dimensoes = array();
                $valores = array();
              
                $total = count ($array)-1;
                $i=0;
                foreach($array as $key=>$value){
                    if (is_array($value)) {
                        $dimensoes[$i] = array2js($value,$show_keys);
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    } else {
                        $dimensoes[$i] = '"'.addslashes($value).'"';
                        if ($show_keys) $dimensoes[$i] = '"'.$key.'":'.$dimensoes[$i];
                    }
                    if ($i==0) $dimensoes[$i] = '{'.$dimensoes[$i];
                    if ($i==$total) $dimensoes[$i].= '}';
                    $i++;
                }
                return implode(',',$dimensoes);
            }
up
-4
sunear at gmail dot com
15 years ago
Made this function to delete elements in an array;

<?php

function array_del_elm($input_array, $del_indexes) {
    if (
is_array($del_indexes)) {
       
$indexes = $del_indexes;
    } elseif(
is_string($del_indexes)) {
       
$indexes = explode($del_indexes, " ");
    } elseif(
is_numeric($del_indexes)) {
       
$indexes[0] = (integer)$del_indexes;
    } else return;
   
$del_indexes = null;
   
   
$cur_index = 0;
    if (
sort($indexes)) for($i=0; $i<count($input_array); $i++) {
        if (
$i == $indexes[$cur_index]) {
           
$cur_index++;
            if (
$cur_index == count($indexes)) return $output_array;
            continue;
        }
       
$output_array[] = $input_array[$i];
    }
    return
$output_array;
}

?>

but then i saw the methods of doing the same by Tyler Bannister & Paul, could see that theirs were faster, but had floors regarding deleting multiple elements thus support of several ways of giving parameters. I combined the two methods to this to this:

<?php

function array_del_elm($target_array, $del_indexes) {
    if (
is_array($del_indexes)) {
       
$indexes = $del_indexes;
    } elseif(
is_string($del_indexes)) {
       
$indexes = explode($del_indexes, " ");
    } elseif(
is_numeric($del_indexes)) {
       
$indexes[0] = (integer)$del_indexes;
    } else return;
    unset(
$del_indexes);
   
    for(
$i=0; $i<count($indexes); $i++) {
        unset(
$target_array[$indexes[$i]]);
    }
    return
$target_array;
}

?>

Fast, compliant and functional ;)
up
-5
webmaster at infoproducts dot x10hosting dot com
15 years ago
New value can also be added to the array as shown below.
$theVariable["google"] = "http//google.com";
or
$theVariable["1"] = "http//google.com";
up
-10
contact at greyphoenix dot biz
16 years ago
<?php
//Creating a multidimensional array

$theVariable = array("Search Engines" =>
array (
   
0=> "http//google.com",
   
1=> "http//yahoo.com",
   
2=> "http//msn.com/"),

"Social Networking Sites" =>
array (
   
0 => "http//www.facebook.com",
   
1 => "http//www.myspace.com",
   
2 => "http//vkontakte.ru",)
);

echo
"The first array value is " . $theVariable['Search Engines'][0];
?>

-- Output--
The first array value is http://google.com
up
-10
gratcypalma at gmail dot com
11 years ago
<?php
function foo() {
    return array(
'name' => 'palma', 'old' => 23, 'language' => 'PHP');
}
/* 1. PHP < 5.4.0 */
$a = foo();
var_dump($a['name']);

/* 2. Works ini PHP >= 5.4.0 */

var_dump(foo()['name']);

/*
When i run second method on PHP 5.3.8 i will be show error message "PHP Fatal error:  Can't use method return value in write context"

http://www.php.net/manual/en/migration54.new-features.php
*/
up
-11
spereversev at envionsoftware dot com
12 years ago
<?php
function array_mask(array $array, array $keys) {
    return
array_intersect_key( $array, array_fill_keys( $keys, 0 ) );
}
?>

Might be helpful to take a part of associative array containing given keys, for example, from a $_REQUEST array

array_mask($_REQUEST, array('name', 'email'));
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-13
thomasdecaux at ebuildy dot com
15 years ago
To browse a simple array:

<?php

foreach ($myArray AS $myItem)
{

}

?>

To browse an associative array:

<?php

foreach ($myArray AS $key=>$value)
{

}

?>

http://www.ebuildy.com
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-15
Jack A
16 years ago
Note that arrays are not allowed in class constants and trying to do so will throw a fatal error.
up
-27
John Marc
14 years ago
Be careful when adding elements to a numeric array.
I wanted to store some info about some items from a database and decided to use the record id as a key.

<?php
$key
=3000000000;
$DATA[$key]=true;
?>

This will create an array of 30 million elements and chances are, you will use up all memory with these 2 lines

<?php
$key
=3000000000;
$DATA["$key"]=true;
?>

This on the other hand will force the array to be an associative array and will only create the one element
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