Trying to learn about php's arrays today.
I have a set of arrays like this:
$a = array (
0 => array ( 'value' => 'America', ),
1 => array ( 'value' => 'England', ),
2 => array ( 'value' => 'Australia', ),
)
$b = array (
0 => array ( 'value' => 'America', ),
1 => arra开发者_Python百科y ( 'value' => 'England', ),
2 => array ( 'value' => 'Canada', ),
)
I need to get the 'new' subarrays that array b brings to the table.
ie, I need to return array ( 'value' => 'Canada', )
I thought I could first merge $a+$b and then compare the result to $a.
$merge = array_merge($a,$b);
$result = array_diff($merge,$a);
But somehow that does not work. It returns array()
How come? And thanks!
This should do the trick:
$new = array();
foreach($b as $elem){
if(!in_array($elem, $a)){
$new[] = $elem;
}
}
Returns Canada.
I'm not a hundred per cent sure on what you are asking. If you want to return the Canada part of array $b in a function you can use
return $b[2]
.
That will return an array containing value=>Canada. If you want to display the content of the array you can use the var_dump function like this.
var_dump($VaribleToDisplay);
var_dump can also be used for other variable types.
If I run your code until array_merge($a, $b)
and do a var_dump($merge)
, I get this:
array(6) {
[0]=>
array(1) {
["value"]=>
string(7) "America"
}
[1]=>
array(1) {
["value"]=>
string(7) "England"
}
[2]=>
array(1) {
["value"]=>
string(9) "Australia"
}
[3]=>
array(1) {
["value"]=>
string(7) "America"
}
[4]=>
array(1) {
["value"]=>
string(7) "England"
}
[5]=>
array(1) {
["value"]=>
string(6) "Canada"
}
}
That's not, what you had in mind.
--
Moreover, array_diff
's documentation on php.net reads:
Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.
Note: This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff($array1[0], $array2[0]);.
Since your array contains subarrays indexed by common keys, you can't use array_merge, array_diff, etc because those deal with arrays indexed by keys (no sub arrays).
You can use array_walk to do what you want, but will take a lot more code. Consider something similar to:
$newVals = array();
function walker($sub, $key, $otherArray)
{
$found = false;
foreach($otherArray as $idx => $sub2)
{
if ($sub['value'] == $sub2['value'])
{
$found = true;
break;
}
}
if (!$found)
$newVals[] = $sub;
}
array_walk($a, 'walker', $b);
This isn't particularly fast. If you can change your input data to use key=>value directly in the array (rather than sub arrays) then array_diff and array_merge will work and will be much faster.
i.e. you would really want to restructure your data like this:
$a = array( 'America', 'Australia', 'Canada' );
Or something similar.
why would you set up your array like that is this for a select or something?
$a = array('countries'=> array('America', 'England', 'Australia'));
$b = array('countries'=> array('America', 'England', 'Canada'));
array_diff($b['countries'], $a['countries']);
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