String Operators
Simple array arithmetic:
A more compact way of adding or subtracting the elements at identical keys...
<?php
function array_add($a1, $a2) { // ...
// adds the values at identical keys together
$aRes = $a1;
foreach (array_slice(func_get_args(), 1) as $aRay) {
foreach (array_intersect_key($aRay, $aRes) as $key => $val) $aRes[$key] += $val;
$aRes += $aRay; }
return $aRes; }
function array_subtract($a1, $a2) { // ...
// adds the values at identical keys together
$aRes = $a1;
foreach (array_slice(func_get_args(), 1) as $aRay) {
foreach (array_intersect_key($aRay, $aRes) as $key => $val) $aRes[$key] -= $val;
foreach (array_diff_key($aRay, $aRes) as $key => $val) $aRes[$key] = -$val; }
return $aRes; }
Example:
$a1 = array(9, 8, 7);
$a2 = array(1=>7, 6, 5);
$a3 = array(2=>5, 4, 3);
$aSum = array_add($a1, $a2, $a3);
$aDiff = array_subtract($a1, $a2, $a3);
// $aSum => [9, 15, 18, 9, 3]
// $aDiff => [9, 1, -4, -9, -3]
?>
To make a similar function, array_concatenate(), change only the first of the two '+=' in array_add() to '.='
Csaba Gabor from Vienna
Array Operators
| Example | Name | Result |
|---|---|---|
| $a + $b | Union | Union of $a and $b. |
| $a == $b | Equality | TRUE if $a and $b have the same key/value pairs. |
| $a === $b | Identity | TRUE if $a and $b have the same key/value pairs in the same order and of the same types. |
| $a != $b | Inequality | TRUE if $a is not equal to $b. |
| $a <> $b | Inequality | TRUE if $a is not equal to $b. |
| $a !== $b | Non-identity | TRUE if $a is not identical to $b. |
The + operator appends elements of remaining keys from the right handed array to the left handed, whereas duplicated keys are NOT overwritten.
<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b; // Union of $a and $b
echo "Union of \$a and \$b: \n";
var_dump($c);
$c = $b + $a; // Union of $b and $a
echo "Union of \$b and \$a: \n";
var_dump($c);
?>
Union of $a and $b: array(3) { ["a"]=> string(5) "apple" ["b"]=> string(6) "banana" ["c"]=> string(6) "cherry" } Union of $b and $a: array(3) { ["a"]=> string(4) "pear" ["b"]=> string(10) "strawberry" ["c"]=> string(6) "cherry" }
Elements of arrays are equal for the comparison if they have the same key and value.
Example #1 Comparing arrays
<?php
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");
var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>
See also the manual sections on the Array type and Array functions.
add a note
User Contributed NotesArray Operators
csaba at alum dot mit dot edu
24-Jun-2008 05:54
24-Jun-2008 05:54
csaba at alum dot mit dot edu
13-Dec-2007 10:42
13-Dec-2007 10:42
Simple array arithmetic:
If you want to add or subtract the elements at identical keys...
<?php
function array_add($a1, $a2) { // ...
// adds the values at identical keys together
$aRes = $a1;
$aRays = func_get_args();
for ($i=1;$i<sizeof($aRays);++$i) {
$aRay = $aRays[$i];
foreach ($aRay as $key => $val)
if (array_key_exists($key, $aRes))
$aRes[$key] += $aRay[$key];
$aRes += $aRay; }
return $aRes; }
function array_subtract($a1, $a2) { // ...
// subtracts the values at identical keys from the corresponding value in $a1
$aRes = $a1;
$aRays = func_get_args();
for ($i=1;$i<sizeof($aRays);++$i) {
$aRay = $aRays[$i];
foreach ($aRay as $key => $val) {
if (array_key_exists($key, $aRes)) $aRes[$key] -= $aRay[$key];
else $aRes[$key] = -$aRay[$key]; } }
return $aRes; }
Example:
$a1 = array(9, 8, 7);
$a2 = array(1=>7, 6, 5);
$a3 = array(2=>5, 4, 3);
$aSum = array_add($a1, $a2, $a3);
$aDiff = array_subtract($a1, $a2, $a3);
// $aSum => [9, 15, 18, 9, 3]
// $aDiff => [9, 1, -4, -9, -3]
?>
To make a similar function, array_concatenate(), change the first += only in array_add() to .=
Csaba Gabor from Vienna
Q1712 at online dot ms
21-Apr-2007 02:54
21-Apr-2007 02:54
The example may get u into thinking that the identical operator returns true because the key of apple is a string but that is not the case, cause if a string array key is the standart representation of a integer it's gets a numeral key automaticly.
The identical operator just requires that the keys are in the same order in both arrays:
<?php
$a = array (0 => "apple", 1 => "banana");
$b = array (1 => "banana", 0 => "apple");
var_dump($a === $b); // prints bool(false) as well
$b = array ("0" => "apple", "1" => "banana");
var_dump($a === $b); // prints bool(true)
?>
puneet singh @ value-one dot com
18-Jan-2006 07:42
18-Jan-2006 07:42
hi just see one more example of union....
<?php
$a = array(1,2,3);
$b = array(1,7,8,9,10);
$c = $a + $b; // Union of $a and $b
echo "Union of \$a and \$b: \n";
//echo $c
print_r($c);
?>
//output
Union of $a and $b: Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 9 [4] => 10 )
kit dot lester at lycos dot co dot uk
21-Aug-2005 06:01
21-Aug-2005 06:01
When comparing arrays that have (some or all) element-values that are themselves array, then in PHP5 it seems that == and === are applied recursively - that is
* two arrays satisfy == if they have the same keys, and the values at each key satisfy == for whatever they happen to be (which might be arrays);
* two arrays satisfy === if they have the same keys, and the values at each key satisfy === for whatever (etc.).
Which explains what happens if we compare two arrays of arrays of arrays of...
Likewise, the corresponding inversions for != <> and !==.
I've tested this to array-of-array-of-array, which seems fairly convincing. I've not tried it in PHP4 or earlier.
kit dot lester at lycos dot co dot uk
21-Aug-2005 05:44
21-Aug-2005 05:44
This manual page doesn't mention < & co for arrays, but example 15-2 in
http://www.php.net/manual/en/language.operators.comparison.php
goes to some lengths to explain how they work.
Peter
29-Oct-2004 04:57
29-Oct-2004 04:57
The code from texbungalow at web dot de below is slightly incorrect. If my memory from primary school history is correct, roman numerals don't allow things like MIM - it has to be MCMXCIX, ie each step is only 1 level down (sorry, I can't explain it very well.
a print_r($segments) comparing the snippets should explain.
Corrected code:
<?php
function roman ($nr ) {
$base_digits= array (
1=> "I",
10=> "X",
100=> "C",
1000=> "M",
);
$help_digits= array (
5=> "V",
50=> "L",
500=> "D",
);
$all_digits= $base_digits+ $help_digits;
foreach ($base_digits as $key1=> $value1 )
foreach ($all_digits as $key2=> $value2 )
if ($key1< $key2 && $key1 >= ($key2 / 10))
$segments[$key2- $key1 ]= $value1. $value2;
$segments+= $all_digits;
krsort ($segments );
foreach ($segments as $key=> $value )
while ($key<= $nr ) {
$nr-= $key;
$str.= $value;
}
return $str;
}
echo roman (1998); // prints MCMXCVIII
?>
dfranklin at fen dot com
22-Apr-2004 10:40
22-Apr-2004 10:40
Note that + will not renumber numeric array keys. If you have two numeric arrays, and their indices overlap, + will use the first array's values for each numeric key, adding the 2nd array's values only where the first doesn't already have a value for that index. Example:
$a = array('red', 'orange');
$b = array('yellow', 'green', 'blue');
$both = $a + $b;
var_dump($both);
Produces the output:
array(3) { [0]=> string(3) "red" [1]=> string(6) "orange" [2]=> string(4) "blue" }
To get a 5-element array, use array_merge.
Dan
texbungalow at web dot de
27-Apr-2003 03:46
27-Apr-2003 03:46
use '+=' to quickly append an array to another one:
function roman ($nr ) {
$base_digits= array (
1=> "I",
10=> "X",
100=> "C",
1000=> "M",
);
$help_digits= array (
5=> "V",
50=> "L",
500=> "D",
);
$all_digits= $base_digits+ $help_digits;
foreach ($base_digits as $key1=> $value1 )
foreach ($all_digits as $key2=> $value2 )
if ($key1< $key2 )
$segments[$key2- $key1 ]= $value1. $value2;
$segments+= $all_digits;
krsort ($segments );
foreach ($segments as $key=> $value )
while ($key<= $nr ) {
$nr-= $key;
$str.= $value;
}
return $str;
}
echo roman (888); // prints DCCCLXXXVIII
amirlaher AT yahoo DOT co SPOT uk
10-Dec-2002 07:41
10-Dec-2002 07:41
[]= could be considered an Array Operator (in the same way that .= is a String Operator).
[]= pushes an element onto the end of an array, similar to array_push:
<?
$array= array(0=>"Amir",1=>"needs");
$array[]= "job";
print_r($array);
?>
Prints: Array ( [0] => Amir [1] => needs [2] => job )