运算符
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数组运算符

数组运算符
例子 名称 结果
$a + $b 联合 $a 和 $b 的联合。
$a == $b 相等 如果 $a 和 $b 具有相同的键／值对则为 TRUE。
$a === $b 全等 如果 $a 和 $b 具有相同的键／值对并且顺序和类型都相同则为 TRUE。
$a != $b 不等 如果 $a 不等于 $b 则为 TRUE。
$a <> $b 不等 如果 $a 不等于 $b 则为 TRUE。
$a !== $b 不全等 如果 $a 不全等于 $b 则为 TRUE。

+ 运算符把右边的数组元素（除去键值与左边的数组元素相同的那些元素）附加到左边的数组后面，但是重复的键值不会被覆盖。

<?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);
?>
执行后，此脚本会显示： 
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"
}

数组中的单元如果具有相同的键名和值则比较时相等。

Example #1 比较数组

<?php
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");

var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>

参见数组类型和数组函数章节。

运算符
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PHP手册 - N: 数组运算符

用户评论:

Dan Patrick (05-Mar-2012 02:39)

It should be mentioned that the array union operator functions almost identically to array_replace with the exception that precedence of arguments is reversed.

cb at netalyst dot com (15-Oct-2008 07:39)

The union operator did not behave as I thought it would on first glance. It implements a union (of sorts) based on the keys of the array, not on the values.

For instance:
<?php
$a = array('one','two');
$b=array('three','four','five');

//not a union of arrays' values
echo '$a + $b : ';
print_r ($a + $b);

//a union of arrays' values
echo "array_unique(array_merge($a,$b)):";
// cribbed from http://oreilly.com/catalog/progphp/chapter/ch05.html
print_r (array_unique(array_merge($a,$b)));
?>

//output

$a + $b : Array
(
    [0] => one
    [1] => two
    [2] => five
)
array_unique(array_merge(Array,Array)):Array
(
    [0] => one
    [1] => two
    [2] => three
    [3] => four
    [4] => five
)

csaba at alum dot mit dot edu (24-Jun-2008 04:54)

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

csaba at alum dot mit dot edu (13-Dec-2007 09:42)

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 01:54)

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 06:42)

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 05:01)

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 04:44)

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 03:57)

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 09:40)

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 02:46)

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 06:41)

[]= 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 )