数组运算符

表格 15-8. 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。

例子 15-5. 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。

add a note User Contributed Notes

puneet singh @ value-one dot com
19-Jan-2006 02:42


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
22-Aug-2005 12:01


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 11:44


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 10:57


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
23-Apr-2004 04:40


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 09:46


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 02:41


[]= 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 )

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