Hi guys I need a bit of help here,
My variable $a has value [{"id":"[1, 2, 3]"}] of type object, now from this I want the first id i.e. in this case I want 1. How can I fetch ut from variable $a?
When I var_dump it prints as below
class Illuminate\Support\Collection#1230 (1) {
protected $items =>
array(1) {
[0] =>
class stdClass#1221 (1) {
public $a =>
string(9) "[1, 2, 3]"
}
}
}
Thank you.
What is the class of $a ?
Is it an extend of Illuminate\Database\Eloquent\Model ?
Maybe this :
$firstId = current($a->id);
EDIT :
I don't see the id on your dump.
current(json_decode($a->first()->id))
or
current(json_decode($a->first()->a))
Can you access ?
echo $a->id; // outputs strings "[1,2,3]"
if yes, then just decode it by using json_decode
$array = json_decode($a->id);
$firstElement = current($array);
Related
I have a weird behavior when assigning an existant object to an array.
In the example below, I have a class that contains one property. I create a first array with 3 instances (let's call them 2-4-6) and then a second array with 2 other instances using one object of the first array (instance 4). While modifying the values of the objects in second array to create 2 new instances (ie instances 3-5), the instance 4 is also modified. In consequence, at the first array query I get the right values (2-4-6) but after creating the second array I get the modified value (2-5-6). I would expect that the assignment operator copied the object, but instead it creates a reference to the instance. In the example I can get rid of this issue by explicitly calling clone, but in a larger scale, this isn't work (wrong code optimization?). Any clue (or good practice) of how to avoid this issue?
Thanks!
<?php
class TestBase
{
private int $m_test = 0;
public function SetTest(int $v)
{
$this->m_test = $v;
}
public function GetTest() : int
{
return $this->m_test;
}
}
function getNewList(TestBase $ref) : array
{
$newlist = [3 => new TestBase(), 5 => $ref];
$newlist[3]->SetTest(3);
$newlist[5]->SetTest(5);
return $newlist;
}
$listOfTest = [2 => new TestBase(), 4 => new TestBase(), 6 => new TestBase()];
$listOfTest[2]->SetTest(2);
$listOfTest[4]->SetTest(4);
$listOfTest[6]->SetTest(6);
foreach ($listOfTest as $test)
{
echo $test->GetTest().'<br>';
}
// 2
// 4
// 6
//$ref = clone $listOfTest[4];
$ref = $listOfTest[4];
$newList = getNewList($ref);
foreach ($listOfTest as $test)
{
echo $test->GetTest().'<br>';
}
// 2
// 5
// 6
?>
The problem is in the way the PHP uses arrays. Array assignment by reference
only works if both the argument and the lvalue are references to arrays. If an object is passed in, it will be copied and a reference to it will be set in both places. The subsequent reassignment of the lvalue will not have any effect on the original array.
Referencing an existing array and then copying it using clone can work around this. The example below shows how this can be done, but you could also use a factory or some other means to create a new array that has references to all of the existing elements (by calling get_object_vars() on each).
<?php
function getNewList(TestBase $ref) : array
{
$newlist = [3 => clone $ref, 5 => clone $ref];
$newlist[3]->SetTest(3);
$newlist[5]->SetTest(5);
return $newlist;
}
//$ref = clone $listOfTest[4];
$ref = &$listOfTest[4];
var_dump($ref); // TestBase Object (1) (2) { ["m_test"]=> int(5) }
//$newList = getNewList($ref);
foreach ($listOfTest as &$test)
{
echo "before: ".$test->GetTest().'<br>'; // 2, 4, 6 in output here!
var_dump($test); // TestBase Object (1) (2) { ["m_test"]=> int(4) }
echo "after: ".$test->GetTest().'<br>'; // 2, 4, 6 in output here!
var_dump($test); // TestBase Object (1) (2) { ["m_test"]=> int(4) }
}
?>
I have this JSON data that is set up as an array of objects that looks like this, where the keys are literally called "key" and the values are literally called "value":
$fruit = [{"key": "a", "value": "apple"},
{"key": "b", "value": "banana"},
{"key": "c", "value": "cherry"}];
I am trying to write a PHP function that takes in this array as an argument, along with the key I want to look up.
The function should act as a lookup so that the function will return the value associated with the provided key. For example:
function lookup($array, $key){
// look through the list of objects and
// return value that is associated with this key
}
Example function call:
lookup($fruit, "c");
Expected output:
"cherry"
I am new to PHP, so I don't know if PHP has a best practice or native function that would make easy work of this, or should I iterate through the $fruit array and build a new PHP array with it first? What is the best way to do this?
Using PHP 7.0+ you can use array_column on an array of objects.
Providing the second argument as the property name to retrieve values from, and then using the third argument to specify the property name to index by, will provide you with a full list of values indexed by the specified key.
Example https://3v4l.org/vJcmH
$values = array_column($json, 'value', 'key');
var_dump($values);
/*
array(3) {
["a"]=>
string(5) "apple"
["b"]=>
string(6) "banana"
["c"]=>
string(6) "cherry"
}
*/
var_dump($values['c']);
/*
string(6) "cherry"
*/
Function usage https://3v4l.org/8TMBf
/**
* #param array|object[] $json
* #param string $key
* #param mixed $default
* #param string $column
* #param string $index
* #return string
*/
function lookup($json, $key, $default = '', $column = 'value', $index = 'key') {
return array_column($json, $column, $index)[$key] ?? $default;
}
var_dump(lookup($json, 'c'));
Result:
string(6) "cherry"
Note, this will return a single value, if you are expecting to have
more than 1 result with the same key property value, this approach
will not yield expected results. If so please let me know and I will update my answer.
Convert your JSON string to a PHP array
$fruit = json_decode($fruit, true);
lookup($fruit, 'key');
Then, you just have to loop through the array in your function.
function lookup($array, $key) {
//loop through all values in array
foreach($array as $values) {
//if 'key' value matches `$key`, return 'value' value.
if($values['key'] == $key) {
return $values['value'];
}
}
//if nothing has been returned, return empty string
return "";
}
Now, if you have control over creating the $fruit value, it would be better to create it in this pattern:
$fruit = [
"a" => "apple",
"b" => "banana",
"c" => "cherry",
];
then you can access it with:
$fruit[$key];
Something like this would work.
https://ideone.com/94Uxby
<?php
$fruit = json_decode($sourceOfJson, true);
function lookup($array, $key){
// Find the index of the entry where "key" = $key
$index = array_search($key, array_column($array, 'key'));
// Handle the entry not being found however you want to.
if(!$index){
return null;
// throw new Exception("Couldn't find index from value $key");
// Log::error("Couldn't find index from value $key");
// return 'SomeDefaultValue';
}
return $array[$index]['value'];
}
echo lookup($fruit, 'c');
Given the following array:
$array = array(
'item_1' => array(
'item_1_1' => array(
'item_1_1_1' => 'Hello',
),
'item_1_2' => 'World',
),
'item_2' => array(),
);
How can I convert that into an Object?
Option 1
$obj = (object) $array;
Or
Option 2
$object = json_decode(json_encode($array), FALSE);
Or something else?
I would like to know the difference in the output between the 2 option and understand the best practice for creating this conversion.
Well you are answering somehow your own question, but if you want to have an object with the attributes like your array you have to cast it, this way an array will remain an array
$obj = (object) $array;
OUTPUT:
object(stdClass)#1 (2) {
["item_1"]=>
array(2) {
["item_1_1"]=>
array(1) {
["item_1_1_1"]=>
string(5) "Hello"
}
["item_1_2"]=>
string(5) "World"
}
["item_2"]=>
array(0) {
}
}
if you are using the json_decode version it will convert arrays to objects too:
object(stdClass)#2 (2) {
["item_1"]=>
object(stdClass)#3 (2) {
["item_1_1"]=>
object(stdClass)#4 (1) {
["item_1_1_1"]=>
string(5) "Hello"
}
["item_1_2"]=>
string(5) "World"
}
["item_2"]=>
array(0) {
}
}
NOTE: just the empty array will be an array here.
To Answer your question: The best practice depends on what YOU need.
It depends, really: if you are working on data that might be an array in one case, and an object the next, it would probably be best to use the json_decode trick, simply because unlike a cast, its result is "recursive". There is one very important thing to keep in mind here, though: numeric indexes can, and probably will cause problems for you at some point in time. Take a look at this bug report
This is documented here, but not in a way that really stands out:
If an object is converted to an array, the result is an array whose elements are the object's properties. The keys are the member variable names, with a few notable exceptions: integer properties are unaccessible;
Exampe of the problem:
$data = [
'foo' => 'bar',
123 => 'all is well',
];
$obj = json_decode(json_encode($data));
var_dump($obj->foo);//bar
var_dump($obj->{123});//all is well
$cast = (array) $obj;
var_dump($cast);//shows both keys
var_dump(isset($cast[123]));//FALSE!!!
var_dump(isset($cast['123']));//FALSE
Basically: If you start converting arrays to objects and back again, numeric keys are not reliable anymore. If I were you, I'd simply change the code that is passing the data where possible, or I'd create a value object that can be set using an array or an object, and normalize the data that way.
Basically how I understand references work is
$a = 5;
$b = &$a;
$a = 10;
echo $b; // 10;
However in this bit of code I'm getting unexpected (for me, which probably has an explanation) result
class Room {
private $users = array();
public function addUser(&$user){
$this->users[] = $user;
}
}
$users = array(
1 => 'Tom',
2 => 'Hank',
3 => 'Sam',
4 => 'John'
);
$room = new Room();
$room->addUser($users[1]);
$room->addUser($users[3]);
unset($users[3]);
echo "<pre>" . print_r($room, true) . "</pre>";
echo "<pre>" . print_r($users, true) . "</pre>";
I expect, after unsetting $users[3], the only user inside of $room to be Tom, but that is not the case, both Tom and Sam are present in the object. Why is unset not affecting the object's property?
EDIT:
Even if I take things a step further with the example and create a class User the effect is still the same
class Room {
private $users = array();
public function addUser(&$user){
$this->users[] = $user;
}
}
class User {
public $name;
function __construct($name){
$this->name = $name;
}
}
$users = array(
1 => new User('Tom'),
2 => new User('Hank'),
3 => new User('Sam'),
4 => new User('John')
);
$room = new Room();
$room->addUser($users[1]);
$room->addUser($users[3]);
unset($users[3]);
echo "<pre>" . print_r($room, true) . "</pre>";
echo "<pre>" . print_r($users, true) . "</pre>";
Unset operates on symbols, not reference targets.
That is why using unset on an undefined variable doesn't raise any kind of error.
$a = 10;
$b = &$a;
unset($b); // forget the name "$b" exists.
echo $a; // 10
If you want to unset it in both places, you have to assign null to one of the variables. This is a "hard unset", as opposed to a "soft unset" which is what you are currently doing.
Also you are not assigning a reference, you're assigning a copy.
$this->users[] = &$user;
Reference Counting Basics :
A PHP variable is stored in a container called a "zval". A zval
container contains, besides the variable's type and value, two
additional bits of information. The first is called "is_ref" and is a
boolean value indicating whether or not the variable is part of a
"reference set". (...) Since PHP allows user-land references, as
created by the & operator, a zval container also has an internal
reference counting mechanism to optimize memory usage. This second
piece of additional information, called "refcount", contains how many
variable names (also called symbols) point to this one zval container.
(...)
Variable containers get destroyed when the "refcount" reaches zero.
The "refcount" gets decreased by one when any symbol linked to the
variable container leaves the scope (e.g. when the function ends) or
when unset() is called on a symbol.
Example with arrays:
<?php
$a = array(
0 => 'aaa',
1 => 'bbb',
2 => 'ccc',
);
debug_zval_dump($a);
// ... string(3) "bbb" refcount(1) ...
$b = array();
$b[0] = &$a[0];
$b[1] = &$a[1];
$a[1] = 'ddd';
debug_zval_dump($a);
// ... &string(3) "bbb" refcount(2) ...
debug_zval_dump($b);
// ... &string(3) "bbb" refcount(2) ...
unset($a[1]);
debug_zval_dump($a);
/*
array(2) refcount(2){
[0]=>
&string(3) "aaa" refcount(2)
[1]=>
&string(3) "ddd" refcount(2)
}
*/
debug_zval_dump($b);
// ... string(3) "ddd" refcount(1) ...
var_dump($a);
/*
array (size=2)
0 => &string 'aaa' (length=3)
2 => string 'ccc' (length=3)
*/
var_dump($b);
/*
array (size=2)
0 => &string 'aaa' (length=3)
1 => string 'ddd' (length=3)
*/
I think there's a slight logical problem between your desired effect and the way you try to do it.
If I understand correctly, you want to assign users to a container, then unsetting one of those user in a way that it will also be unsetted in your container. This
unset($users[3]);
unsets the value of the fourth element of your users array.
if we did $user[3] = 'foo'; the value contained in the corresponding container's entry will be set to 'foo' as well, but the container's index key itself will not get unset, or affected by the reference, because it is not part of the referenced value
If you want to unset the user, either you keep track of which index key is assigned to which user in your container and then delete users with this index key, or you set the value of $users[3] to null (or whatever suits your needs) and skip the null values when dealing with your container
You can change a value of arrays, like this:
CODE:
private $users = array();
public function addUser(&$user){
$this->users[] = &$user;
}
}
$users = array(
1 => 'Tom',
2 => 'Hank',
3 => 'Sam',
4 => 'John'
);
$room = new Room();
$room->addUser($users[1]);
$room->addUser($users[3]);
$users[3] = "AAA123";
echo "<pre>" . print_r($room, true) . "</pre>";
echo "<pre>" . print_r($users, true) . "</pre>";
OUTPUT:
Room Object
(
[users:Room:private] => Array
(
[0] => Tom
[1] => AAA123
)
)
Array
(
[1] => Tom
[2] => Hank
[3] => AAA123
[4] => John
)
But delete it's not possible this way... I don't know how to explain, so just give example:
$a = 10;
$b = &$a;
unset($a);
echo $b; // 10
Then you deleting variable name, you not delete zval(container), until refcount reach 0... then "Garbage Collection" do all work and delete zval...
So method unset() remove variable name only in this case...
Be careful.
You are passing to addUser() a reference to the string 'Tom' allocated while building the array $users.
First, addUser() should read $this->users[] =& $user;, otherwise you will be copying the value into $this->users[] instead of sharing the reference.
Now, both $users and Room::$users share the same objects, however unset($users[3]) removes the element mapped by the index 3 from the array, it does not destroy the mapped object.
I'm working on a project in CodeIgniter 2 and now I'm stuck on the most basic of concepts.
Model:
Get an object array from my table which contains all rows that match a specific value for a field named foo. There can be one or more rows that match. In this example, two rows.
public function get_sample($foo)
{
$query = $this->db->get_where('sample_db', array('foo' => $foo));
return $query->result();
}
Controller:
Assign the results and make output available to view.
public function view($foo)
{
$data['array'] = $this->sample_model->get_sample($foo);
$this->load->view('view', $data);
}
View:
echo var_dump($array); // for testing
echo $array[1]->text
var_dump() of $array:
array(2) {
[0]=> object(stdClass)#23 (4) {
["id"]=> string(1) "1"
["foo"]=> string(3) "bar"
["number"]=> string(4) "1234"
["text"]=> string(23) "This is content in 1234"
}
[1]=> object(stdClass)#24 (4) {
["id"]=> string(1) "2"
["foo"]=> string(3) "bar"
["number"]=> string(4) "9999"
["text"]=> string(23) "This is content in 9999"
}
}
The rendered ouput of echo $array[1]->text; is: This is content in 9999
And I understand how all that is working: $array[1]->text is the content of the text field in the array object with the index of 1, my second object.
However, I have a field called number and I want to access the object with a certain number and get its corresponding text value.
Example: How can I retrieve the value of text where the number is 9999? I cannot use $array[1]->text since I can never be sure of the object's position in the array. Something like $array['number' => '9999']->text, but I know that's not right. Maybe I need to loop through the array looking for a match?
This looks so simple yet everything I've tried has failed and resulted in various PHP errors. I've been studying the PHP manual here and here, but cannot seem to find anything about what I'm looking to do, or maybe I'm just misapplying what I'm reading. Any guidance is appreciated.
In addition to an answer using best practices following the MVC model, I'm hoping for a link to the proper page in the documentation, as well as pointing out any errors in my wording/terminology above.
EDIT:
This answer contains the actual code I used to solve my problem. Although, Yagi's answer was accepted because it put me in the right direction.
How about using this :
foreach ($array as $row) {
if ($row->number == '9999') {
echo $row->text;
}
}
Loop through the array, and find the number object value of 9999 and get the text
Why don't you just to a query and search for that number (or order by that number?)
Either way, what you need is a multidimensional array search function (that iterates through array of object and returns the found field value combo )
Something like this (put this in helper)
function multi_array_search($array, $field, $value)
{
$results = array();
if (is_array($array))
{
if ($array->$field == $value) //chek the filed against teh value, you can do addional check s(i.e. if field has been set)
$results[] = $array;
foreach ($array as $subarray)
$results = array_merge($results, multi_array_search($subarray, $key, $value)); //recurisve serach
}
return $results;
}
//than in view or in controller, depending where you need it
$result = multi_array_search($array, "number", "9999");
var_dump($result) will return or whether number of foudn instances
array() {
[0]=> object(stdClass)#24 (4) {
["id"]=> string(1) "2"
["foo"]=> string(3) "bar"
["number"]=> string(4) "9999"
["text"]=> string(23) "This is content in 9999"
}
}
you might be looking for something like this...
array_filter($array, function($o){ return $o->number == 9999; } );
http://php.net/manual/en/function.array-filter.php
EDIT
$o is the parameter in the callback function. each element of the array is passed to the callback function. if the function returns false, the element will be filtered out.
$arr = array(
(object) array(
'num' => 33,
'text' => 'hello',
),
(object) array(
'num' => 44,
'text' => 'world',
),
);
$filtered = array_filter($arr, function($o){ return $o->num == 33; });
echo $filtered[0]->text; // hello
as you stated, index will remain, so use array_values or array_shift. here's an example with function
function get_by_num($arr, $num){
return array_shift(array_filter($arr, function($o) use ($num) { return $o->num == $num; }));
}
$obj = get_by_num($arr, 44);
var_dump($obj);
// object(stdClass)#2 (2) { ["num"]=> int(44) ["text"]=> string(5) "world" }
in this case $obj will be either NULL if element is not found, or the first match. $num is transferred along so you can use any value. you can even improve it:
function get_first_match($arr, $field, $val){
return array_shift(array_filter($arr, function($o) use ($field, $val) { return $o->{$field} == $val; }));
}
$obj = get_first_match($arr, 'num', 44);
and now you can search any field. in your case
$obj = get_first_match($array, 'number', 9999);
Thanks to Yagi's answer, I came up with the following very simple solution. I loop through the array and assign the value of text to a new array with an index that matches the value of number. Then in the view file, I can access the text value based on this index.
Controller:
public function view($foo)
{
$data['array'] = $this->sample_model->get_sample($foo);
foreach ($data['array'] as $row) {
$data['result'][$row->number] = $row->text;
};
$this->load->view('view', $data);
}
View:
if (isset($result[9999])) echo $result[9999];