Array Operators

Table 15-7. 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 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);

?>

When executed, this script will print the following:


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 15-4. 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.

User Contributed Notes
Array Operators

Peter
29-Oct-2004 09:57


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 03:40


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
26-Apr-2003 08:46


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 12:41


[]= 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 )