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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附加到左边的数组后面,两个数组中都有的键名,则只用左边数组中的,右边的被忽略。
<?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" }
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。
[#1] Anonymous [2014-01-29 00:23:31]
The manual say ...
"The + operator appends the right elements in the array from left, whereas duplicated keys are NOT overwritten"
but ..
$a = array("a" => 'A', "b" => 'B');
$b = array("a" => 'A', "b" => 'B', "c" => 'C');
$c = $a + $b // or $b + a is the same output;
echo '<pre>';
print_r($c);
echo '<pre>';
//Output for $a + b or $b + a
Array (
[a] => A
[b] => B
[c] => C
)
[#2] sd6733531 at gmail dot com [2013-03-30 07:18:12]
Look out use + with array combine.
$arr = array(1, 2, 3);
$int=345;
$arr=$arr+$int;
Of couse,use + to combine array is easy and readable.
But if one of the variable is not array type(like above code) ,that would make a PHP Fatal Error:
PHP Fatal error: Unsupported operand types
Maybe should do check before.
[#3] Dan Patrick [2012-03-04 18:39:01]
It should be mentioned that the array union operator functions almost identically to array_replace with the exception that precedence of arguments is reversed.
[#4] cb at netalyst dot com [2008-10-15 11:39:13]
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 + $b : Array
(
[0] => one
[1] => two
[2] => five
)
array_unique(array_merge(Array,Array)):Array
(
[0] => one
[1] => two
[2] => three
[3] => four
[4] => five
)
[#5] csaba at alum dot mit dot edu [2008-06-24 08:54:14]
Simple array arithmetic:
A more compact way of adding or subtracting the elements at identical keys...
<?php
function array_add($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
[#6] Q1712 at online dot ms [2007-04-20 17:54:27]
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)
?>
[#7] puneet singh @ value-one dot com [2006-01-18 10:42:58]
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 )
[#8] kit dot lester at lycos dot co dot uk [2005-08-21 09:01:56]
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.
[#9] kit dot lester at lycos dot co dot uk [2005-08-21 08:44:12]
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.
[#10] dfranklin at fen dot com [2004-04-22 13:40:32]
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
[#11] amirlaher AT yahoo DOT co SPOT uk [2002-12-09 22:41:51]
[]= 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:
<?php
$array= array(0=>"Amir",1=>"needs");
$array[]= "job";
print_r($array);
?>
Prints: Array ( [0] => Amir [1] => needs [2] => job )