Stumped by this one:
I have a function that returns an array of folders in a given directory. When I iterate through the array, I can see all the items. However, if I try to print the first item, I get nothing:
function get_folders($dir) {
return array_filter(scandir($dir), function ($item) use ($dir) {
return (is_dir($dir.'/'.$item) && $item != "." && $item != "..") ;
});
}
$folders = get_folders(".");
$first_folder = $folders[0];
echo $first_folder; // returns blank.
Interestingly, if I don't filter out the "." and "..", then $first_folder does print ".". Can anyone explain this?
As noted in the manual: Array keys are preserved when using array_filter().
The keys are preserved from the call to scandir() which will include the . and .. directories, meaning your filtered array will start at 2 or more (whatever the key is for the first directory).
A simple fix would be to wrap the whole thing in array_values() to get the resultant array having keys starting from 0 and incrementing by one.
return array_values(array_filter(...));
If you don't actually care about the keys, then basic array functions could be of use like key or current.
From the array_filter manual:
Iterates over each value in the input array passing them to the callback function. If the callback function returns true, the current value from input is returned into the result array. Array keys are preserved.
So, scandir($dir) gets you an array with . at key 0, thus if you later filter . out, there will be nothing at key 0 in the result.
If you want to know what the first key of the resulting array is, try the array_keys function.
EDIT: actually, salathe's suggestion to use array_values is better in your case than getting the keys from array_keys.
can you print the folders and see if there is some key you can get the first folder with as opposed to selecting the index of zero? It seems lke $folders[0] would work unless the entries are stored with a different set of indexes / keys.
Try doing a
print_r($folders)
to see if it outputs your first folder and all other folders as expected with the corresponding indexes you're looking for.
array_filter preserves array keys, so if the first two elements have been removed, then the "new first" element has an index of 2. To convert that into an array indexed starting from 0, use array_values:
return array_values(array_filter(scandir($dir), function ($item) use ($dir) {
...
As others have said, array_filter preserves the keys in the array. Given that initially the item '.' has key 0, the filtered array ends up not having any item with key 0 (you can verify this with print_r($folders). So this line:
$first_folder = $folders[0];
ends up generating an E_NOTICE saying that there is no key 0 in the array (having notices turned on would alert you to the cause of the problem immediately, I highly recommend it) and giving $first_folder the value null.
To get the first value of the filtered array, regardless of key, use reset:
$first_folder = reset($folders);
if($first_folder === false) {
echo 'No folders!';
}
else {
echo 'First folder: '.$first_folder;
}
Related
I'm trying to store the users's input via the method get in an array to store it and further process it without overwriting the initial get-value. But I dont know how.. do I have to store them in a database to do that? Or can I just push every input into an array?
I believe the following should work for you... This will take all the $_GETs that you supply and put them in a new array so you can modify them without affecting the original $_GET array.
if(is_array($_GET)){
$newArr = $_GET; // modify $newArr['postFieldName'] instead of $_GET['postFieldName'] to preserve original $_GET but have new array.
}
That solution there will dupe the $_GET array. $_GET is just an internal PHP array of data, as is $_POST. You could also loop through the GETs if you do not need ALL of the GETs in your new array... You would do this by setting up an accepted array of GETs so you only pull the ones you need (this should be done anyways, as randomly accepting GETs from a form can lead to some trouble if you are also using the GETs for database/sql functions or anything permission based).
if(is_array($_GET) && count($_GET) > 0){
$array = array();
$theseOnly = array("postName", "postName2");
foreach($_GET as $key => $value){
if(!isset($array[$key]) && in_array($key, $theseOnly)){ // only add to new array if they are in our $theseOnly array.
$array[$key] = $value;
}
}
print_r($array);
} else {
echo "No $_GET found.";
}
I would just add to what #Nerdi.org said.
Specifically the second part, instead of looping through the array you can use either array_intersect_key or array_diff_key
$theseOnly = array("postName", "postName2");
$get = array_intersect_key( $_GET, array_flip($theseOnly);
//Or
$get = array_diff_key( $_GET, array_flip($theseOnly);
array_intersect_key
array_intersect_key() returns an array containing all the entries of array1 which have keys that are present in all the arguments.
So this one returns only elements you put in $theseOnly
array_diff_key
Compares the keys from array1 against the keys from array2 and returns the difference. This function is like array_diff() except the comparison is done on the keys instead of the values.
So this one returns the opposite or only elements you don't put in $theseOnly
And
array_flip
array_flip() returns an array in flip order, i.e. keys from array become values and values from array become keys.
This just takes the array of names with no keys (it has numeric keys by default), and swaps the key and the value, so
$theseOnly = array_flip(array("postName", "postName2"));
//becomes
$theseOnly = array("postName"=>0, "postName2"=>1);
We need the keys this way so they match what's in the $_GET array. We could always write the array that way, but if your lazy like me then you can just flip it.
session_start();
if(!isset($_SESSION['TestArray'])) $_SESSION['TestArray'] = array();
if(is_array($_GET)){
$_SESSION['TestArray'][] = $_GET;
}
print_r($_SESSION['TestArray']);
Thanks everybody for helping! This worked for me!
I have a need to check if the elements in an array are objects or something else. So far I did it like this:
if((is_object($myArray[0]))) { ... }
However, on occasion situations dictate that the input array does not have indexes that start with zero (or aren't even numeric), therefore asking for $myArray[0] will generate a Notice, but will also return the wrong result in my condition if the first array element actually is an object (but under another index).
The only way I can think of doing here is a foreach loop where I would break out of it right on the first go.
foreach($myArray as $element) {
$areObjects = (is_object($element));
break;
}
if(($areObjects)) { ... }
But I am wondering if there is a faster code than this, because a foreach loop seems unnecessary here.
you can use reset() function to get first index data from array
if(is_object(reset($myArray))){
//do here
}
You could get an array of keys and get the first one:
$keys = array_keys($myArray);
if((is_object($myArray[$keys[0]]))) { ... }
try this
reset($myArray);
$firstElement = current($myArray);
current gets the element in the current index, therefore you should reset the pointer of the array to the first element using reset
http://php.net/manual/en/function.current.php
http://php.net/manual/en/function.reset.php
How can I tell if array element, in foreach loop, has a key?
Some code:
function test($p_arr){
foreach ($p_arr as $key => $value){
// detect here if key 'came with the array' or not
}
}
$arr1['a'] = 10;
$arr2[] = 10;
$arr3[2] = 10;
test($arr1); // yes
test($arr2); // no
test($arr3); // yes
edit #1
I am aware that $arr2 also as an automated index-key. I need to know if it is automated or not.
edit #2
My use of it is simple.
In the function, I create a new array and use the $key as the new $key, if it was provided by the function call. or the $value as the new $key, if it was omitted in the function call.
I know that I can just force the use of key to each element, but in some parts of the code, the data structure itself is very dynamic* - and i'm trying to stay flexible as much as possible.
*code that create other code, that create ... and so on.
There is no difference between explicit keys and implicit keys generated via []. The [] doesn't mean "give this element no key", it means "use the next key for this element".
Every element has a key
$arr1['a'] = 10; // key is the string 'a'
$arr2[] = 10; // key is will be the integer zero
$arr3[2] = 10; // key is the integer 2
Edit
Perhaps it would be good to understand why you wish to know if the index is automated or not? It seems odd.
Every array created has to have a key, whether it's a integer or string as the key or index, without no index the PHP would have no way to interpret or even pull information from the array it's self.
$Var = array ("String","anotherstring","sdfhs","dlj");
the above array will automatically be generated with a numeric index starting from 0.
$Array = array();
$Array[] = "This is a string";
The above will push information into the array, as there has been no index or key specified. It will automatically be assigned with the closest numeric value to 0, which does not already exist in the array.
$Array = array();
$Array['key'] = "This is another string";
The above will push information into the array also, but as we have specified an index with a string representation rather an automatically assigned value.
So the answer to your question, if i'm reading this Correctly.
If your referring to check if the array values are specified by PHP/The Code prior to reading the array. There is no soundproof method, as everything would need to be assigned to the array before it has data. further more, if your only adding elements to the array with a string key, then yes. It is possible.
If your relying on automatically generated numeric values, or assigning your own numeric values. it's impossible to tell if PHP has assigned this automatically, or you have specified.
Delete an element from an array in php without array_search
I want to delete an array element from array, but I dont know the array key of that element only value is known
It is possible by array_search with value, first to find the key and then use unset
Is there any inbuilt array function to remove array element with array value ?
You can only remove element from array only by referencing to this KEY. So you have to get this KEY somehow. The function to get the key for the searched value from array is exactly array_search() function which returns KEY for given VALUE.
Any function that has to "to remove array element with array value" will have to perform a loop over every* element looking for the value to delete. Therefore you might as well just add your own for loop to do this, or array_search() will do this for you.
The reason arrays have keys is so that you can get at values efficiently using that key.
*actually you'd stop looping once you'd found it rather than keep looking, unless there could be duplicates to remove
Example showing one way you can do this without using array_search()
$myArray = array(5, 4, 3, 2, 1, 0, -1, -2);
$knownValue = 3;
$myArray = array_filter(
$myArray,
function($value) use ($knownValue) {
return $value !== $knownValue;
}
);
The only valid case to not use array_search is if you'd like to unset several values. You still need to use keys though. I'd recommend you to iterate through the array and remove fields that match your criteria.
foreach($array as $key => $value) {
if($value === $deleteValue)
unset($array[$key]);
}
I'm trying to understand why, on my page with a query string,
the code:
echo "Item count = " . count($_GET);
echo "First item = " . $_GET[0];
Results in:
Item count = 3
First item =
Are PHP associative arrays distinct from numeric arrays, so that their items cannot be accessed by index? Thanks-
They can not. When you subscript a value by its key/index, it must match exactly.
If you really wanted to use numeric keys, you could use array_values() on $_GET, but you will lose all the information about the keys. You could also use array_keys() to get the keys with numerical indexes.
Alternatively, as Phil mentions, you can reset() the internal pointer to get the first. You can also get the last with end(). You can also pop or shift with array_pop() and array_shift(), both which will return the value once the array is modified.
Yes, the key of an array element is either an integer (must not be starting with 0) or an associative key, not both.
You can access the items either with a loop like this:
foreach ($_GET as $key => $value) {
}
Or get the values as an numerical array starting with key 0 with the array_values() function or get the first value with reset().
You can do it this way:
$keys = array_keys($_GET);
echo "First item = " . $_GET[$keys[0]];
Nope, it is not possible.
Try this:
file.php?foo=bar
file.php contents:
<?php
print_r($_GET);
?>
You get
Array
(
[foo] => bar
)
If you want to access the element at 0, try file.php?0=foobar.
You can also use a foreach or for loop and simply break after the first element (or whatever element you happen to want to reach):
foreach($_GET as $value){
echo($value);
break;
}
Nope -- they are mapped by key value pairs. You can iterate the they KV pair into an indexed array though:
foreach($_GET as $key => $value) {
$getArray[] = $value;
}
You can now access the values by index within $getArray.
As another weird workaround, you can access the very first element using:
print $_GET[key($_GET)];
This utilizes the internal array pointer, like reset/end/current(), could be useful in an each() loop.