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

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User Contributed Notes 14 notes

down

2 months ago

Be careful with type hints in callbacks when using array-traverse functions. In some cases, this may silently cause the data type of elements to change. 

<?php
declare(strict_types=1);

// Missing fatal TypeError, No side effects
$unexpected = array_filter(['123', (string) PHP_INT_MAX], fn (int $item) => true);
var_dump($unexpected);

// Missing fatal TypeError, Typecasting side effect
$unexpectedTypecasting = array_map(fn (int $item) => $item, ['123', (string) PHP_INT_MAX]);
var_dump($unexpectedTypecasting);

// Missing fatal TypeError, Typecasting side effect
$unexpectedTypecasting = array_map(fn (string $item) => $item, [123, PHP_INT_MAX]);
var_dump($unexpectedTypecasting);

// Missing fatal TypeError, Typecasting side effect
$unexpectedTypecasting = array_reduce(['123', (string) PHP_INT_MAX], fn (?int $carry, int $item) => $item);
var_dump($unexpectedTypecasting);

$bigIntValue = bcadd((string) PHP_INT_MAX, '1');
// Fatal TypeError
$expectedTypeError = array_map(fn (int $item) => $item, [$bigIntValue]);
var_dump($expectedTypeError);
?>

The above example will output (PHP version 8.3.6, error_reporting E_ALL):

<?php
array(2) {
  [0]=>
  string(3) "123"
  [1]=>
  string(19) "9223372036854775807"
}
array(2) {
  [0]=>
  int(123)
  [1]=>
  int(9223372036854775807)
}
array(2) {
  [0]=>
  string(3) "123"
  [1]=>
  string(19) "9223372036854775807"
}
int(9223372036854775807)

Fatal error: Uncaught TypeError: {closure}(): Argument #1 ($item) must be of type int, string given
?>

down

permanovd at gmail dot com ¶

6 years ago

A simple trick that can help you to guess what diff/intersect or sort function does by name.

[suffix] assoc - additional index check. Compares both value and index.

Example: array_diff_assoc, array_intersect_assoc.

[suffix] key - index only check. Ignores value of array, compares only indexes.

Example: array_diff_key, array_intersect_key.

[suffix] **empty** - no "key" or "assoc" word in suffix. Compares values only. Ignores indexes of array.

Example: array_diff, array_intersect.

[prefix] u - will do comparison with user defined function. Letter u can be used twice in some functions (like array_udiff_uassoc), this means that you have to use 2 functions (one for value, one for index).

Example: array_udiff_uassoc, array_uintersect_assoc.

This also works with array sort functions:

[prefix] a - associative. Will preserve keys.

Example: arsort, asort.

[prefix] k - key sort. Will sort array by keys.

Example: uksort, ksort.

[prefix] r - reverse. Will sort array in reverse order.

Example: rsort, krsort.

[prefix] u - sort by user defined function (same as for diff/intersect). 

Example: usort, uasort.

down

renatonascto at gmail dot com ¶

15 years ago

Big arrays use a lot of memory possibly resulting in memory limit errors. You can reduce memory usage on your script by destroying them as soon as you´re done with them. I was able to get over a few megabytes of memory by simply destroying some variables I didn´t use anymore. 
You can view the memory usage/gain by using the funcion memory_get_usage(). Hope this helps!

down

-1

indioeuropeo at driverop dot com ¶

5 years ago

I need to take an element from the Array and change its position within the Array by moving the rest of the elements as required.
This is the function that does it. The first parameter is the working Array. The second is the position of the element to move and the third is the position where to move the element.
The function returns the modified Array.
<?php
function array_move_elem($array, $from, $to) {
    if ($from == $to) { return $array; }
    $c = count($array);
    if (($c > $from) and ($c > $to)) {
        if ($from < $to) {
            $f = $array[$from];
            for ($i = $from; $i < $to; $i++) {
                $array[$i] = $array[$i+1];
            }
            $array[$to] = $f;
        } else {
            $f = $array[$from];
            for ($i = $from; $i > $to; $i--) {
                $array[$i] = $array[$i-1];
            }
            $array[$to] = $f;
        }
        
    }
    return $array;
}

?>
Examples:
<?php
$array = array('Cero','Uno','Dos','Tres','Cuatro','Cinco','Seis','Siete','Ocho','Nueve','Diez');
$array = array_move_elem($array, 3, 5); // Move element in position 3 to position 5...
print_r($array);

$array = array_move_elem($array, 5, 3); // Move element in position 5 to position 3, leaving array as it was... ;)
print_r($array);

?>
Return:
<?php
Array ( [0] => Cero [1] => Uno [2] => Dos [3] => Cuatro [4] => Cinco [5] => Tres [6] => Seis [7] => Siete [8] => Ocho [9] => Nueve [10] => Diez )
Array ( [0] => Cero [1] => Uno [2] => Dos [3] => Tres [4] => Cuatro [5] => Cinco [6] => Seis [7] => Siete [8] => Ocho [9] => Nueve [10] => Diez )
?>

down

-10

nicoolasens at gmail dot com ¶

8 years ago

/*to change an index without rewriting the whole table and leave at the same place.
*/
<?php
function change_index(&$tableau, $old_key, $new_key) {
    $changed = FALSE;
    $temp = 0;
    foreach ($tableau as $key => $value) {
        switch ($changed) {
            case FALSE :
                //creates the new key and deletes the old
                if ($key == $old_key) {
                    $tableau[$new_key] = $tableau[$old_key];
                    unset($tableau[$old_key]);
                    $changed = TRUE;
                }
                break;

            case TRUE :
                //moves following keys
                if ($key != $new_key){
                $temp= $tableau[$key];
                unset($tableau[$key]);
                $tableau[$key] = $temp;
                break;
                }
                else {$changed = FALSE;} //stop
        }
    }
    array_values($tableau); //free_memory
}

//Result : 
$tableau = array(1, 2 , 3, 4,5, 6, 7, 8, 9, 10);
$res = print_r($tableau, TRUE);
$longueur = strlen($res) -1;
echo "Old array :\n" . substr($res, 8, $longueur) . "\n" ;

change_index ($tableau, 2, 'number 2');
$res = print_r($tableau, TRUE);
$longueur = strlen($res) -10;
echo "New array :\n" . substr($res, 8, $longueur) . "\n" ;

/*
Old array :
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
)

New array :
    [0] => 1
    [1] => 2
    [numéro 2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9
    [9] => 10
*/
?>

down

-16

info at hotkey404 dot com ¶

3 years ago

Updated code of 'indioeuropeo' with option to input string-based keys.

INPUT:
array(4) {
  ["a"]=>
  string(5) "Apple"
  ["b"]=>
  string(6) "Banana"
  ["c"]=>
  string(3) "Cat"
  ["d"]=>
  string(3) "Dog"
}

OUTPUT:
array(4) {
  ["a"]=>
  string(5) "Apple"
  ["d"]=>
  string(3) "Dog"
  ["b"]=>
  string(6) "Banana"
  ["c"]=>
  string(3) "Cat"
}

FUNCTION:
<?php
function array_move_elem($array, $from, $to){
// return if non-numeric couldn't be found or from=to
    if(!is_numeric($from)){
        if(array_search($from, array_keys($array))!==FALSE){
            $from = array_search($from, array_keys($array));
        }else{
            return $array;
        }
    }
    $array_numeric_keys = array();
    foreach($array as $k => $v){
        $array_numeric_keys[] = $k;
    }
    if ($from == $to) { return $array; }
    $c = count($array_numeric_keys);
    if (($c > $from) and ($c > $to)) {
        if ($from < $to) {
            $f = $array_numeric_keys[$from];
            for ($i = $from; $i < $to; $i++) {
                $array_numeric_keys[$i] = $array_numeric_keys[$i+1];
            }
            $array_numeric_keys[$to] = $f;
        } else {
            $f = $array_numeric_keys[$from];
            for ($i = $from; $i > $to; $i--) {
                $array_numeric_keys[$i] = $array_numeric_keys[$i-1];
            }
            $array_numeric_keys[$to] = $f;
        }
       
    }
    $array_new = array();
    foreach($array_numeric_keys as $v){
        $array_new[$v] = $array[$v];
    }
    return $array_new;
}
?>

down

-26

kolkabes at googlemail dot com ¶

12 years ago

Short function for making a recursive array copy while cloning objects on the way.

<?php
function arrayCopy( array $array ) {
        $result = array();
        foreach( $array as $key => $val ) {
            if( is_array( $val ) ) {
                $result[$key] = arrayCopy( $val );
            } elseif ( is_object( $val ) ) {
                $result[$key] = clone $val;
            } else {
                $result[$key] = $val;
            }
        }
        return $result;
}
?>

down

-23

ob at babcom dot biz ¶

17 years ago

Here is a function to find out the maximum depth of a multidimensional array.

<?php
// return depth of given array
// if Array is a string ArrayDepth() will return 0
// usage: int ArrayDepth(array Array)

function ArrayDepth($Array,$DepthCount=-1,$DepthArray=array()) {
  $DepthCount++;
  if (is_array($Array))
    foreach ($Array as $Key => $Value)
      $DepthArray[]=ArrayDepth($Value,$DepthCount);
  else
    return $DepthCount;
  foreach($DepthArray as $Value)
    $Depth=$Value>$Depth?$Value:$Depth;
  return $Depth;
}
?>

down

-27

dave at davidhbrown dot us ¶

12 years ago

While PHP has well over three-score array functions, array_rotate is strangely missing as of PHP 5.3. Searching online offered several solutions, but the ones I found have defects such as inefficiently looping through the array or ignoring keys. 

The following array_rotate() function uses array_merge and array_shift to reliably rotate an array forwards or backwards, preserving keys. If you know you can trust your $array to be an array and $shift to be between 0 and the length of your array, you can skip the function definition and use just the return expression in your code.

<?php
function array_rotate($array, $shift) {
    if(!is_array($array) || !is_numeric($shift)) {
        if(!is_array($array)) error_log(__FUNCTION__.' expects first argument to be array; '.gettype($array).' received.');
        if(!is_numeric($shift)) error_log(__FUNCTION__.' expects second argument to be numeric; '.gettype($shift)." `$shift` received.");
        return $array;
    }
    $shift %= count($array); //we won't try to shift more than one array length
    if($shift < 0) $shift += count($array);//handle negative shifts as positive
    return array_merge(array_slice($array, $shift, NULL, true), array_slice($array, 0, $shift, true));
}
?>
A few simple tests:
<?php
$array=array("foo"=>1,"bar"=>2,"baz"=>3,4,5);

print_r(array_rotate($array, 2));
print_r(array_rotate($array, -2));
print_r(array_rotate($array, count($array)));
print_r(array_rotate($array, "4"));
print_r(array_rotate($array, -9));
?>

down

-17

DamianKaelGreen at gmail dot com ¶

7 years ago

While there are a lot of array functions in the PHP libs, there also seem to be a lot of rudimentary ones missing.

I went ahead and created several of my own functions for handling multiple non-associative (na) arrays including:

na_array_merge 
na_array_intersect
na_array_diff
na_array_xnor
na_array_xor

If you are using Venn diagrams to think about your arrays, then these functions might be for you. 

I have made them available and posted documentation for them here: https://www.greendingle.com/some-useful-non-associative-array-functions/

down

-25

Ewan ¶

7 years ago

I was looking for an array aggregation function here and ended up writing this one.

Note: This implementation assumes that none of the fields you're aggregating on contain The '@' symbol.

<?php
  function array_group_by($flds, $arr) {
    $groups = array();
    foreach ($arr as $rec) {
      $keys = array_map(function($f) use($rec) { return $rec[$f]; }, $flds);
      $k = implode('@', $keys);
      if (isset($groups[$k])) {
        $groups[$k][] = $rec;
      } else {
        $groups[$k] = array($rec);
      }
    }
    return $groups;
  }

?>

down

-26

oliverSPAMMENOT at e-geek dot com dot au ¶

14 years ago

Function to pretty print arrays and objects. Detects object recursion and allows setting a maximum depth. Based on arraytostring and u_print_r from the print_r function notes. Should be called like so: 



<?php

egvaluetostring($value)   //no max depth, or

egvaluetostring($value, $max_depth)   //max depth set



function egvaluetostring($value, $max_depth, $key = NULL, $depth = 0, $refChain = array()) {

  if($depth > 0)

    $tab = str_repeat("\t", $depth);

  $text .= $tab . ($key !== NULL ? $key . " => " : "");

  

  if (is_array($value) || is_object($value)) {

    $recursion = FALSE;

    if (is_object($value)) {

      foreach ($refChain as $refVal) {

        if ($refVal === $value) {

          $recursion = TRUE;

          break;

        }

      }

      array_push($refChain, $value);

    }

    

    $text .= (is_array($value) ? "array" : "object") . " ( ";

    

    if ($recursion) {

      $text .= "*RECURSION* ";

    }

    elseif (isset($max_depth) && $depth >= $max_depth) {

      $text .= "*MAX DEPTH REACHED* ";

    }

    else {

      if (!empty($value)) {

        $text .= "\n";

        foreach ($value as $child_key => $child_value) {

          $text .= egvaluetostring($child_value, $max_depth, (is_array($value) ? "[" : "") . $child_key . (is_array($value) ? "]" : ""), $depth+1, $refChain) . ",\n";

        }

        $text .= "\n" . $tab;

      }

    }

    

    $text .= ")";

    

    if (is_object($value)) {

      array_pop($refChain);

    }

  }

  else {

    $text .= "$value";

  }



  return $text;

}

?>

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-30

mo dot longman at gmail dot com ¶

16 years ago

to 2g4wx3:
i think better way for this is using JSON, if you have such module in your PHP. See json.org.

to convert JS array to JSON string: arr.toJSONString();
to convert JSON string to PHP array: json_decode($jsonString);

You can also stringify objects, numbers, etc.

down

-29

cyberchrist at futura dot net ¶

16 years ago

Lately, dealing with databases, I've been finding myself needing to know if one array, $a, is a proper subset of $b.

Mathematically, this is asking (in set theory) [excuse the use of u and n instead of proper Unicode):
 
( A u B ) n ( ~ B )

What this does is it first limits to known values, then looks for anything outside of B but in the union of A and B (which would be those things in A which are not also in B).

If any value exists in this set, then A is NOT a proper subset of B, because a value exists in A but not in B.  For A to be a proper subset, all values in A must be in B.

I'm sure this could easily be done any number of ways but this seems to work for me.  It's not got a lot of error detection such as sterilizing inputs or checking input types.

// bool array_subset( array, array )
// Returns true if $a is a proper subset of $b, returns false otherwise.

function array_subset( $a, $b )
{
    if( count( array_diff( array_merge($a,$b), $b)) == 0 )
        return true;
    else
        return false;
}

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Array Functions

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User Contributed Notes 14 notes