This question already has answers here:
Closed 11 years ago.
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PHP Arrays: A good way to check if an array is associative or sequential?
Hello :)
I was wondering what is the shortest (best) way to check if an array is
a list:
array('a', 'b', 'c')
or it's an associative array:
array('a' => 'b', 'c' => 'd')
fyi: I need this to make a custom json_encode function
function is_assoc($array){
return array_values($array)!==$array;
}
Note that it will also return TRUE if array is indexed but contains holes or doesn't start with 0, or keys aren't ordered. I usually prefer using this function because it gives best possible performance.
As an alternative for these cases I prefer this (just keep in mind that it's almost 4 times slower than above):
function is_assoc($array){
return !ctype_digit( implode('', array_keys($array)) );
}
Using ksort() as Rinuwise commented is a bit slower.
Related
This question already has answers here:
Using a string path to set nested array data [duplicate]
(8 answers)
Closed 4 years ago.
Edit (after downvote): There is a similar question here > Using a string path to set nested array data
However I didn't find that question when searching for an answer due to the way it's worded, and I'm sure this will happen for other people, so this question may act as a useful gateway to that question and it's answers.
I'm sure I'm missing something obvious, but I can't think how to do this: I have an array containing one or more items:
array('value1', 'value2');
I need to use these values as the keys in a multidimensional array :
array['value1']['value2'] = 'somevalue';
How do I do this?
You can use a nice recursion here:
function nestArray($items, $value) {
return $items ?
array($items[0] => nestArray(array_slice($items, 1), $value))
: $value;
}
$array = array('value1', 'value2');
print_r(nestArray($array, 'somevalue'));
This question already has answers here:
php array difference against keys of an array and an array of keys?
(3 answers)
Unset elements using array keys
(2 answers)
Closed 5 years ago.
I am attempting to mirror the behavior of newArray = oldArray, with the caveat of excluding some key/values of the oldArray, so something like newArray = oldArray - undesiredOldKeyValue. I realize this is fully doable with a foreach on the oldArray and using an if to see if the encountered key is desired or not, but I am interested in a simpler or more concise approach if possible.
A couple of things to keep in mind, I need to exclude key/value pairs based on key, not value. I do not want to modify the oldArray in the process of doing this.
You may try to use array_filer. Something like:
$new_array = array_filter($old_array, function ($value, $key) {
// return false if you don't want a value, true if you want it.
// Example 1: `return $value != 'do not keep this one';`
// Example 2: `return !in_array($key, ['unwanted-key1', 'unwanted-key2', 'etc']);`
}, ARRAY_FILTER_USE_BOTH);
It will filters elements of an array using a callback function.
This question already has answers here:
Are PHP Associative Arrays ordered?
(4 answers)
Closed 8 years ago.
I'm learning PHP and I've got a question that's bothering me. PHP arrays seem to be hashmaps internally. If you give an array a key and value, it almost certainly has to put the key through some sort of hashing function before placing it in an actual array, right? Why then, if I give an array a series of keys and values and then dump these to screen, does PHP maintain the order in which I entered the values?
for instance:
$arr = array();
$arr[1] = 'one';
$arr[3] = 'three';
$arr[2] = 'two';
foreach($arr as $key => $val)
echo "$key => $val<br>"
would render "1 => one, 2 => two, 3 => three" in a typical hashmap, but instead I get "1 => one, 3 => three, 2 => two." Which to me means that there have to be both and order and a key being maintained in whatever datatype this actually is.
Thanks in advance for any explanation.
You are correct about the array being stored as a hash table or ordered map. Basically, everything in PHP is a hash table.
See here: Understanding PHP's internal array implementation
This question already has answers here:
Characters allowed in php array keys?
(11 answers)
Closed 8 years ago.
I am studying PHP and came across a question like this:
What is the output of the following array?
Code:
$a = array(0.001 => 'b', .1 => 'c');
print_r($a);
The answer is 0 => 'c' - now I know array keys can't be numbers but wouldn't that throw an error? Why is the first element overwritten?
From the documentation on arrays:
Floats are also cast to integers, which means that the fractional part will be truncated. E.g. the key 8.7 will actually be stored under 8.
and, as Alex points out below:
If multiple elements in the array declaration use the same key, only the last one will be used as all others are overwritten.
This question already has answers here:
comparing arrays in php, without caring for the order
(6 answers)
Closed 9 years ago.
I'm trying solving a problem where i need to check if the arrays are same no matter how they are sorted i cannot use sorting because it add extra over head to time this function is taking in answering.
I am currently using array_diff_assoc
$arr1 = array(1,2,3);
$arr2 = array(3,2,1);
$result = array_diff_assoc($arr1,$arr2);
print_r($result);
Array
(
[0] => 1
[2] => 3
)
But the above arrays are same!! The human way.
Any idea for comparing two arrays.
Well interpreter is not human right ? ;)
Even if you do a simple var_dump($arr1==$arr2) on your existing array, it will return false.
This below code returns true !
$arr1 = array(1,2,3);
$arr2 = array(2=>3,1=>2,0=>1);//position is same as yours., i've just set a key
var_dump($arr1==$arr2); //true