stricly speaking / best practice: do I need to set up every 'deeper nested sub array' or can you just access it?
//so do I need to do this:
if(!isset($multiArray[$newKey])) $multiArray[$newKey] = array();
//before I can do this?
$multiArray[$newKey][] = 'somevalue';
Strictly speaking no, PHP will create the new array before pushing the value to it, without any problem.
Best practice? It's probably personal opinion based, I would say create the array first for readability and it makes sense logically. If another developer picks up your code, it might not be obvious that you are creating a new array, as opposed to pushing to an existing array.
It is not necessary to initialize variables in PHP however it is a very good practice. Uninitialized variables have a default value of their type depending on the context in which they are used - booleans default to FALSE, integers and floats default to zero, strings (e.g. used in echo) are set as an empty string and arrays become to an empty array.
Source : PHP Manual http://fr2.php.net/manual/en/function.array-multisort.php
Related
Let's say I have a variable which is an initialized, empty array.
$cache = [];
The data in this array can be created like this, for example (please excuse the crude code and variable/key names, they're here for the sake of this example only):
for ($row in $someOtherArray) {
$cache[$row['id']][] = $row['data'];
}
Since $cache is a PHP array, I don't really need to initialize $cache[$row['id']] to also be an array. However, I sometimes encounter code like this:
for ($row in $someOtherArray) {
if (!isset($cache[$row['id']])) {
$cache[$row['id']] = [];
}
$cache[$row['id']][] = $row['data'];
}
Above, the sub-array is explicitly initialized as an empty array. Is it useful somehow? For example - does it help the interpreter in some way? Or is it only a developer being overzealous?
It's unnecessary as far as PHP is concerned. PHP will implicitly create any number of sub-arrays for you using the $foo[$bar][] syntax. It may be required for business logic, though not in this particular arrangement; it's simply redundant here. If the value assignment is somehow separate logic, but you still want to ensure that at least an empty array exists for the key, that's the only time it makes sense.
Once you have initialised a variable as an array, you can use array specific methods on that variable. For example array_push(), array_map() etc..
I am trying to deal with some input that may or may not be an array, with the intent of obtaining the first item if the input is an array, and the item itself otherwise.
Here is how I was planning to go about it:
$payload = ((array)json_decode($mapOrArray))[0];
This did not sit well with the interpreter, however. Instead, I am currently using this:
$payload = array_values((array)json_decode($mapOrArray))[0];
Only once I've wrapped the casted array in a useless method call can I use this approach.
Is accessing an index of the result of a cast impossible with a single statement? If so, what is a better way to deal with this task, preferably without introducing an extraneous variable?
list($payload) = (array) json_decode($mapOrArray);
One thing that's always bugged me (and everyone else, ever) about PHP is its inconsistency in function naming and parameters. Another more recent annoyance is its tendency to ask for function parameters by reference rather than by value.
I did a quick browse through the PHP manual, and found the function sort() as an example. If I was implementing that function I'd take an array by value, sort it into a new array, and return the new value. In PHP, sort() returns a boolean, and modifies the existing array.
How I'd like to call sort():
$array = array('c','a','b');
$sorted_array = sort($array);
How PHP wants me to call sort():
$array = array('c','a','b');
sort($array);
$sorted_array = $array;
And additionally, the following throws a fatal error: Fatal error: Only variables can be passed by reference
sort(array('c','a','b');
I'd imagine that part of this could be a legacy of PHP's old days, but there must have been a reason things were done this way. I can see the value in passing an object by reference ID like PHP 5+ does (which I guess is sort of in between pass by reference and pass by value), but not in the case of strings, arrays, integers and such.
I'm not an expert in the field of Computer Science, so as you can probably gather I'm trying to grasp some of these concepts still, and I'm curious as to whether there's a reason things are set up this way, or whether it's just a leftover.
The main reason is that PHP was developed by C programmers, and this is very much a C-programming paradigm. In C, it makes sense to pass a pointer to a data structure you want changed. In PHP, not so much (Among other things, because references are not the same as a pointer).
I believe this is done for speed-reason.
Most of the time you need the array you are working on to be sorted, not a copy.
If sort should have returned a new copy of the array then for each time you call sort(); the PHP engine should have copied the array into new one (lowering speed and increasing space cost) and you would have no way to control this behaviour.
If you need the original array to be not sorted (and this doesn't happen so often) then just do:
$copy = $yourArray;
sort($yourArray);
this is my first question.
I am doing some optimizations on a php script, improving its speed of execution...
Between :
$datas = array();
$datas['file_import'] = $file_name_reporting;
And :
unset($datas);
$datas['file_import'] = $file_name_reporting;
Can someone tell me which one is faster ?
Thank you
Your second example causes warning, because $datas is right now null and you are treating it as an array, so you have to declare it as an empty array before.
So just follow your first example - assign an empty array and then put into it some data.
array() will create an array whereas unset() will destroy a variable.
I think first method is just a overwriting but second one includes deleting, checking existence, triggering warning and creating new array
It's ridiculous to claim that either form is "faster" than the other. Both versions will execute so fast that you would need to run them millions of times inside a loop to perhaps notice a difference. Do you actually do that inside your script? If not, forget about "optimization" here (actually, it would be a good idea to forget about all optimization "by eye", as any experienced developer can tell you).
On top of that, the two versions actually do different things, in that unset will remove the name $datas from the sumbol table (and give you a notice in the next line when you attempt to add a value to an array).
Just use what feels right, and look inside heavy loops to find something to optimize.
In both cases, a new Array will be constructed. Unsetting a variable in php, will set it's value to null, only to call the array constructor on the next line. Although I agree with knittl, my suggestion would be:
$datas = array('file_import' => $file_name_reporting);
By creating a new array, you automatically 'unset' the variable, and by passing values to the array constructor, you can fill your array with whatever values you want while you're at it.
Obviously the first code will work faster because you do only two operations: explicitly create an array and add a portion of data. The second example will cause a warning because you destroy a variable and then try to use it again.
Additionally unset will not release used memory, it will only release a pointer on variable. Memory will be released when gc will be runned. To release a memory, use $datas = null; instead.
What would you say is the most efficient way to get a single value out of an Array. I know what it is, I know where it is. Currently I'm doing it with:
$array = unserialize($storedArray);
$var = $array['keyOne'];
Wondering if there is a better way.
You are doing it fine, I can't think of a better way than what you are doing.
You unserialize
You get an array
You get value by specifying index
That's the way it can be done.
Wondering if there is a better way.
For the example you give with the array, I think you're fine.
If the serialized string contains data and objects you don't want to unserialize (e.g. creating objects you really don't want to have), you can use the Serialized PHP library which is a complete parser for serialized data.
It offers low-level access to serialized data statically, so you can only extract a subset of data and/or manipulate the serialized data w/o unserializing it. However that looks too much for your example as you only have an array and you don't need to filter/differ too much I guess.
Its most efficient way you can do, unserialize and get data, if you need optimize dont store all variables serialized.
Also there is always way to parse it with regexp :)
If you dont want to unseralize the whole thing (which can be costly, especially for more complex objects), you can just do a strpos and look for the features you want and extract them
Sure.
If you need a better way - DO NOT USE serialized arrays.
Serialization is just a transport format, of VERY limited use.
If you need some optimized variant - there are hundreds of them.
For example, you can pass some single scalar variable instead of whole array. And access it immediately
I, too, think the right way is to un-serialize.
But another way could be to use string operations, when you know what you want from the array:
$storedArray = 'a:2:{s:4:"test";s:2:"ja";s:6:"keyOne";i:5;}';
# another: a:2:{s:4:"test";s:2:"ja";s:6:"keyOne";s:3:"sdf";}
$split = explode('keyOne', $storedArray, 2);
# $split[1] contains the value and junk before and after the value
$splitagain = explode(';', $split[1], 3);
# $splitagain[1] should be the value with type information
$value = array_pop(explode(':', $splitagain[1], 3));
# $value contains the value
Now, someone up for a benchmark? ;)
Another way might be RegEx ?