what is the best way to access all the elements of the object instead of using foreach?
Thanks in advance...
get_object_vars — Gets the properties of the given object
details - http://php.net/manual/en/function.get-object-vars.php
What's wrong with foreach?
Well but there are several methods
You could do something like:
$length = count($arr);
for($i = 0; $i<$length; $i++)
you could also do
while($i < $length)
and access the items directly if you do have numeric keys.
However foreach won't be slower and its the best way to go if you don't have numeric keys.
You can also access the items using next($arr) or you can push/pop
I would say it depends on the context what you want to do.
If you want to do X operations with an array of size X for example you need some loop.
If yuo only want to apply the very same operation on all elements you can use the handy function array_map
if you just want to get all information from it you could also use get_object_vars however, then you have just a new array and what then?
It really depends on the context what you want to do!
In most cases foreach is fine and fast.
If you want to search for specific keys/values or see whether they exists, there are special optimized array functions for that,.
Related
Bear with me, I'm learning.
I often see snippets like the one below:
<?p
$imageArray = get_field('image_field');
$imageAlt = $imageArray['alt'];
$imageURL = $imageArray['url'];
?>
It is pedagogical and clear and organized. But is it necessary to get the entire array before querying the array for values? Can I not define the variable in just a single line? Something like the below (which doesn't work, neither the other variants I have tried):
$imageAlt = get_field('image_field', ['alt']);
$imageURL = get_field('image_field', ['url']);
Yes, you can.
As of PHP 5.4 it is possible to array dereference the result of a function or method call directly. Before it was only possible using a temporary variable. - Source
$imageAlt = get_field('image_field')['alt'];
https://eval.in/548036
The question you are asking can be answered by asking 2 questions:
Is it doable ?
Is it a good idea to do it that way ?
Is it doable ?
Yes! You do not have to store the array in a variable and re-use it later.
For instance, you could do:
$imageAlt = get_field('image_field')['alt'];
Note: This will work in PHP 5.4+ and is called: Array dereferencing.
But that is not the only consideration...
Is it a good idea to do it that way ?
No. It's not a good idea in many cases. The get_field() function, depending on your context, is probably doing a lot of work and, each time you call it, the same work is don multiple times.
Let's say you use the count() function. It will count the number of items in an array. To do that, it must iterate through all items to get the value.
If you use the count() function each time you need to validate number of items in an array, you are doing the task of counting each and every time. If you have 10 items in your array, you probably won't notice. But if you have thousands of items in your array, this may cause a delay problem to compute your code (a.k.a. it will be slow).
That is why you would want to do something like: $count = count($myArray); and use a variable instead of calling the function.
The same applies to your question.
While PHP 5.4+ allows you to directly dereference a function return value like this:
get_field('image_field')['alt']
...in this particular case I would not suggest you do so, since you're using two values from the resulting array. A function call has a certain overhead just in itself, and additionally you don't know what the function does behind the scenes before it returns a result. If you call the function twice, you may incur a ton of unnecessary work, where a single function call would have done just as well.
This is not to mention keeping your code DRY; if you need to change the particulars of the function call, you now need to change it twice...
PHP allows you to play around quite a bit:
function foo(){
return array('foo' => 1, 'bar' => 2);
}
Option 1
echo foo()['foo']; // 1
# Better do this if you plan to reuse the array value.
echo ($tmp = foo())['foo']; // 1
echo $tmp['bar']; // 2
It is not recommended to call a function that returns an array, to specifically fetch 1 key and on the next line doing the same thing.
So it is better to store the result of the function in a variable so you can use it afterwards.
Option 2
list($foo, $bar) = array_values(foo());
#foo is the first element of the array, and sets in $foo.
#bar is the second element, and will be set in $bar.
#This behavior is in PHP 7, previously it was ordered from right to left.
echo $foo, $bar; // 12
Option 3
extract(foo()); // Creates variable from the array keys.
echo $foo, $bar;
extract(get_field('image_field'));
echo $alt, $url;
Find more information on the list constructor and extract function.
Instead of working with mysql data, I have created csv file that I plan to use as the source of data for content, etc.
And I have successfully been able to parse the csv and store it into a complex array, that has the following header row aka the keys for the arrays.
"Title","Year","Rated","Released","Runtime","Genre","Director","Writer","Actors","Plot","Language","Country","Awards","Poster","Metascore","imdbRating","imdbVotes","imdbID","Type","Response"
My current stage is to allow dynamic ajax sorting of the arrays.
I have two fields, that I am allowing sorting at the beginning, "Year" and "Title".
So I pass different url paramters, such as "yearasc" or "yeardesc" or "titleasc" or "titledesc".
Then try to sort for that.
So what I did reading a different so post, was to do this.
First I create new arrays that only store the key fields, I need for sorting.
Then based on what sort type, do a different array_multisort.
array_multisort($year, SORT_ASC, $all_rows);
But what I get is results that multiple dupplicate data.
But I wonder if having the first row, be the header row, which is required by the function I pass the data after any sorting to, is causing issues with array sorting.
For simple array sorting, existing functions makes sense and work fine.
But for complicated ones, it is just complex to even understand how to approach solving this problem.
Any suggestions, thoughts or ideas are appreciated and thanked.
Thank you!
I don't have the actual code that is probably going to help you, but I do have a suggestion as for how you can tackle this and make it work..
Keep it simple. First, create your own CSV with just 1 header (Year or Title ) that you want to sort on.
Write your code to sort on that.
Then, add the other one ( Title if you used Year before, or Year if you used Title before ) and sort on whichever you want.
Then, add one more header (say, Rated) that you don't want to sort on.
You should then be able to work with the original CSV.
I'd try to write simple methods and keep your processing to a minimum in each one.
I hope that helps. I realize its more philosophical of an answer, so it is hit or miss if it helps you get the job done. Just realize that this approach will, indeed, take a little more time to write - but the point behind it is that you're taking out all of the "noise" that's getting in your way first. It helps you look at only your problem first and solve that.
You can set a custom sort function to the array. Use asort() if you need to keep original array keys.
<?php
$sortfields = array('year', 'bleh');
function cmp($a, $b) {
global $sortfields;
foreach ($sortfields as $sortfield) {
$cmp = strcmp($a[$sortfield], $b[$sortfield]);
// if desc, invert sign of $cmp
if ($cmp !== 0)
return $cmp;
}
return 0;
}
usort($all_rows, "cmp");
The function usort() calls a user defined comparison function, which returns the same logic from strcmp function: 0 if equal, < 0 is $a is less than $b and > 0 if $a is greater than $b.
This function will compare each field set in $sortfields variable, if it find any comparison that is different (in the order set), it will immediately return the difference.
I need to create an association between an Array and a Number; as PHP lacks a Map type, I am trying using an array to achieve this:
$rowNumberbyRow = array();
$rowNumberByRow[$rowData] = $rowNumber;
However, when I evaluate the code, I get the following Error:
Warning: Illegal offset type
Just to note, the data stored in the array ($rowData) does not have any 'unique' values that I can use as a key for the $rowNumberByRow Array.
Thanks!
UPDATE:
To answer some of my commenters, I am trying to create a lookup table so that my application can find the row number for a given row in O(1) time.
PHP does have a map Class: It's called SplObjectStorage. It can be accessed with exactly the same syntax as a general array is (see Example #2 on the reference).
But to use the class you will have to use the ArrayObject class instead of arrays. It is handled exactly the same way arrays are and you can construct instances from arrays (e.g. $arrayObject = new ArrayObject($array)).
If you don't want to use those classes, you can also just create a function that creates unique hash-strings for your indexes. For example:
function myHash($array){
return implode('|',$array);
}
$rowNumberByRow[myHash($array)] = $rowNumber;
You will of course have to make sure that your hashes are indeed unique, and I would strongly suggest you use the SplObjectStorage and maybe read a little bit more about the SPL classes of php.
Why not just store the row number in the array? e.g:
$rowData['rowNumber'] = $rowNumber;
You could instead serialize the array, e.g:
$rowNumberByRow[serialize($rowData)] = $rowNumber;
However that's pretty inefficient.
In php you can use only scalar values as an array keys.
If your $rowNumber is unique - then you'd try to use the opposite relation direction. If it is not unique - then you don't have any possible solution I know.
The answer has been alredy given and accepted, but while i was searching for a similar problem, i found this question, and i felt like i should drop a line: when someone wants to use an array with values as keys for another array, it would be useful to use the function array_combine.
If i got the arrays correctly, you could use:
$rowNumberByRow = array_combine($rowData, $rowNumber);
Please take a look at the PHP manual to see some info about permitted values for the keys :)
Does count() really count the all the elements of a PHP array, or is this value cached somewhere and just gets retrieved?
Well, we can look at the source:
/ext/standard/array.c
PHP_FUNCTION(count) calls php_count_recursive(), which in turn calls zend_hash_num_elements() for non-recursive array, which is implemented this way:
ZEND_API int zend_hash_num_elements(const HashTable *ht)
{
IS_CONSISTENT(ht);
return ht->nNumOfElements;
}
So you can see, it's O(1) for $mode = COUNT_NORMAL.
In PHP 5+ the length is stored in the array so the counting is not done each time.
EDIT: You also might find this analysis interesting: PHP Count Performance. Although the length of the array is maintained by the array, it still seems as though it is faster to hold on to it if you are going to call count() many times.
PHP stores the size of an array internally, but you're still making a function call when which is slower than not making one, so you'll want to store the result in a variable if you're doing something like using it in a loop:
For example,
$cnt = count($array);
for ($i =0; $i < $cnt; $i++) {
foo($array[$i]);
}
Additionally, you can't always be sure count is being called on an array. If it's called on an object that implements Countable for example, the count method of that object will be called.
Is there a way to get the the current position of an array from within a nested array ?
I have a php script that has a for loop which cycles through an array, with in this is an nested loop which cycle through a sub array.
I can use pos() to get the position of the child array, is there anyway of getting the current position of the parent array.
I am sure there must be a way to do this, or is the best way to just create a counter?
thanks in advance
.k
If you're using a for loop, you already have a counter. In this example, it's $i :
for($i = 0; $i < $arrayLength; $i++) ...
If you're actually using a foreach loop, use the syntax that gives you the key:
foreach($array as $key => $value) ...
A PHP variable has no information from where it is referenced - due to references and copy-on-write there might be even more things (global/local variables, array elements, properties, ...) pointing to a single variables.
If you have a reference to the "parent" element you can use pos() on that, if not you have to handle this yourself.