Is this the simplest way there is for getting rid of duplicate strlen items from an array?
I do alot of programming that do similar tasks as this, thats why Im asking, if Im doing it too complicated, or if this is the easiest way.
$usedlength = array();
$no_duplicate_filesizes_in_here = array();
foreach ($files as $file) {
foreach ($usedlength as $length) {
if (strlen($file) == $length) continue 2;
}
$usedlength[] = strlen($file);
$no_duplicate_filesizes_in_here[] = $file;
}
$files = $no_duplicate_filesizes_in_here;
There's not a lot hugely wrong with looping manually, though your example could be:
$files = array_intersect_key($files, array_unique(array_map('strlen', $files)));
PHP has a plethora of useful array functions available.
You can try this:
$no_duplicate_filesizes_in_here = array();
for ($i=count($files)-1;$i>=0;$i--){
$no_duplicate_filesizes_in_here[strlen($files[$i])] = $file;
}
$files = array_values($no_duplicate_filesizes_in_here);
// if you don't care about the keys, don't bother with array_values()
If you're using PHP 5.3 or above, array_filter provides a nice syntax for doing this:
$nodupes = array_filter($files, function($file) use (&$lengths) {
if (in_array(strlen($file), (array) $lengths)) {
return false;
}
$lengths[] = strlen($file);
return true;
});
Not as short as some other answers, but another aproach would be to use a key-based lookup:
$used = array();
$no_dupes = array();
foreach ($files as $file) {
if ( !array_key_exists(($length = strlen($file)), $used) ) {
$used[$length] = true;
$no_dupes[] = $file;
}
}
This would have the added bonus of not wasting time on storing duplicates (only to overwrite them later), however, whether this loop would be faster than some of PHP's built in array methods is probably down to a number of factors (number of duplicates, length of files array and so on) and would need to be tested. The above is what I would assume to be quicker in most cases, but I'm not a processor ;)
The above also means the first file found is the one that is kept, rather than the last found in some of the other approaches.
Related
I have a JSON file with around 30 sub sections. Each subsection will be different. I wanted to convert the data inside it into a format i wanted. The code works fine. But i feel its not optimized 100%.
Client1Insurance, Client2Insurance, ClientFInsurance, FamilyInsurance, Client1Pension, Client2Pension, ClientFPension, FamilyPension.
Above is an example of how this JSON would look like. All above are arrays which have sub arrays inside them. There are around 30 arrays like this.
foreach ($json as $item) {
if (strpos($crmMapKey, "Insurance")) {
$returnArray[] = $this->handleInsurance($item);
} elseif (strpos($crmMapKey, "Pension")) {
$returnArray[] = $this->handlePension($item);
} ... continues the comparison till the json ends
}
I need a way to avoid this long if else comparions which I am not proud of. Will someone be able to suggest a better way to do this?
Thanks.
If they are named the same as you show in your code, something containing Insurance will call handleInsurance, etc. then just get the term and use it in the method call:
preg_match('/Insurance|Pension/', $crmMapKey, $match);
$returnArray[] = $this->{'handle'.$match[0]}($item);
If not then you can use a lookup array:
$lookup = ['Insurance' => 'doSomething', 'Pension' => 'doAnotherThing'];
preg_match('/Insurance|Pension/', $crmMapKey, $match);
$returnArray[] = $this->{'handle'.$lookup[$match[0]]}($item);
Or use the keys in the pattern so you only have to modify the array:
preg_match('/'.implode('|', array_keys($lookup)).'/', $crmMapKey, $match);
The switch I mentioned in a comment might not be the best but works:
switch(true) {
case strpos($crmMapKey, "Insurance") !== false;
$returnArray[] = $this->handleInsurance($item);
break;
case strpos($crmMapKey, "Pension") !== false;
$returnArray[] = $this->handlePension($item);
break;
//etc...
}
Another way would be to call variable based functions.
foreach ($json as $item) {
$returnArray[] = $crmMapKey($item);
}
function Client1Insurance($item) {
// Do something in here.
return $array;
}
function Client2Insurance($item) {
// Do something in here.
return $array;
}
Much more elegant way of doing things I feel.
I have a PHP array that I'd like to duplicate but only copy elements from the array whose keys appear in another array.
Here are my arrays:
$data[123] = 'aaa';
$data[423] = 'bbb';
$data[543] = 'ccc';
$data[231] = 'ddd';
$data[642] = 'eee';
$data[643] = 'fff';
$data[712] = 'ggg';
$data[777] = 'hhh';
$keys_to_copy[] = '123';
$keys_to_copy[] = '231';
$keys_to_copy[] = '643';
$keys_to_copy[] = '712';
$keys_to_copy[] = '777';
$copied_data[123] = 'aaa';
$copied_data[231] = 'ddd';
$copied_data[643] = 'fff';
$copied_data[712] = 'ggg';
$copied_data[777] = 'hhh';
I could just loop through the data array like this:
foreach ($data as $key => $value) {
if ( in_array($key, $keys_to_copy)) {
$copied_data[$key] = $value;
}
}
But this will be happening inside a loop which is retrieving data from a MySQL result set. So it would be a loop nested within a MySQL data loop.
I normally try and avoid nested loops unless there's no way of using PHP's built-in array functions to get the result I'm looking for.
But I'm also weary of having a nested loop within a MySQL data loop, I don't want to keep MySQL hanging around.
I'm probably worrying about nested loop performance unnecessarily as I'll never be doing this for more than a couple of hundred rows of data and maybe 10 keys.
But I'd like to know if there's a way of doing this with built-in PHP functions.
I had a look at array_intesect_key() but that doesn't quite do it, because my $keys_to_copy array has my desired keys as array values rather than keys.
Anyone got any ideas?
Cheers, B
I worked it out - I almost had it above.I thought I'd post the answer anyway for completeness. Hope this helps someone out!
array_intersect_key($data, array_flip($keys_to_copy))
Use array_flip() to switch $keys_to_copy so it can be used within array_intersect_keys()
I'll run some tests to compare performance between the manual loop above, to this answer. I would expect the built-in functions to be faster but they might be pretty equal. I know arrays are heavily optimised so I'm sure it will be close.
EDIT:
I have run some benchmarks using PHP CLI to compare the foreach() code in my question with the code in my answer above. The results are quite astounding.
Here's the code I used to benchmark, which I think is valid:
<?php
ini_set('max_execution_time', 0);//NOT NEEDED FOR CLI
// BUILD RANDOM DATA ARRAY
$data = array();
while ( count($data) <= 200000) {
$data[rand(0, 500000)] = rand(0, 500000);
}
$keys_to_copy = array_rand($data, 100000);
// FOREACH
$timer_start = microtime(TRUE);
foreach ($data as $key => $value) {
if ( in_array($key, $keys_to_copy)) {
$copied_data[$key] = $value;
}
}
echo 'foreach: '.(microtime(TRUE) - $timer_start)."s\r\n";
// BUILT-IN ARRAY FUNCTIONS
$timer_start = microtime(TRUE);
$copied_data = array_intersect_key($data, array_flip($keys_to_copy));
echo 'built-in: '.(microtime(TRUE) - $timer_start)."s\r\n";
?>
And the results...
foreach: 662.217s
array_intersect_key: 0.099s
So it's much faster over loads of array elements to use the PHP array functions rather than foreach. I thought it would be faster but not by that much!
Why not load the entire result set into an array, then begin processing with nested loops?
$query_result = mysql_query($my_query) or die(mysql_error());
$query_rows = mysql_num_rows($query_result);
for ($i = 0; $i < $query_rows; $i++)
{
$row = mysql_fetch_assoc($query_result);
// 'key' is the name of the column containing the data key (123)
// 'value' is the name of the column containing the value (aaa)
$data[$row['key']] = $row['value'];
}
foreach ($data as $key => $value)
{
if ( in_array($key, $keys_to_copy))
{
$copied_data[$key] = $value;
}
}
I have a large array.
In this array I have got (among many other things) a list of products:
$data['product_name_0'] = '';
$data['product_desc_0'] = '';
$data['product_name_1'] = '';
$data['product_desc_1'] = '';
This array is provided by a third party (so I have no control over this).
It is not known how many products there will be in the array.
What would be a clean way to loop though all the products?
I don't want to use a foreach loop since it will also go through all the other items in the (large) array.
I cannot use a for loop cause I don't know (yet) how many products the array contains.
I can do a while loop:
$i = 0;
while(true) { // doing this feels wrong, although it WILL end at some time (if there are no other products)
if (!array_key_exists('product_name_'.$i, $data)) {
break;
}
// do stuff with the current product
$i++;
}
Is there a cleaner way of doing the above?
Doing a while(true) looks stupid to me or is there nothing wrong with this approach.
Or perhaps there is another approach?
Your method works, as long as the numeric portions are guaranteed to be sequential. If there's gaps, it'll miss anything that comes after the first gap.
You could use something like:
$names = preg_grep('/^product_name_\d+$/', array_keys($data));
which'll return all of the 'name' keys from your array. You'd extract the digit portion from the key name, and then can use that to refer to the 'desc' section as well.
foreach($names as $name_field) {
$id = substr($names, 12);
$name_val = $data["product_name_{$id}"];
$desc_val = $data["product_desc_{$id}"];
}
How about this
$i = 0;
while(array_key_exists('product_name_'.$i, $data)) {
// loop body
$i++;
}
I think you're close. Just put the test in the while condition.
$i = 0;
while(array_key_exists('product_name_'.$i, $data)) {
// do stuff with the current product
$i++;
}
You might also consider:
$i = 0;
while(isset($data['product_name_'.$i])) {
// do stuff with the current product
$i++;
}
isset is slightly faster than array_key_exists but does behave a little different, so may or may not work for you:
What's quicker and better to determine if an array key exists in PHP?
Difference between isset and array_key_exists
Is it possible to have an AND in a foreach loop?
For Example,
foreach ($bookmarks_latest as $bookmark AND $tags_latest as $tags)
You can always use a loop counter to access the same index in the second array as you are accessing in the foreach loop (i hope that makes sense).
For example:-
$i = 0;
foreach($bookmarks_latest as $bookmark){
$result['bookmark'] = $bookmark;
$result['tag'] = $tags_latest[$i];
$i++;
}
That should achieve what you are trying to do, otherwise use the approach sugested by dark_charlie.
In PHP 5 >= 5.3 you can use MultipleIterator.
Short answer: no. You can always put the bookmarks and tags into one array and iterate over it.
Or you could also do this:
reset($bookmarks_latest);
reset($tags_latest);
while ((list(, $bookmark) = each($bookmarks_latest)) && (list(,$tag) = each($tags_latest)) {
// Your code here that uses $bookmark and $tag
}
EDIT:
The requested example for the one-array solution:
class BookmarkWithTag {
public var $bookmark;
public var $tag;
}
// Use the class, fill instances to the array $tagsAndBookmarks
foreach ($tagsAndBookmarks as $bookmarkWithTag) {
$tag = $bookmarkWithTag->tag;
$bookmark = $bookmarkWithTag->bookmark;
}
you can't do that.
but you can
<?php
foreach($keyval as $key => $val) {
// something with $key and $val
}
the above example works really well if you have a hash type array but if you have nested values in the array I recommend you:
or option 2
<?php
foreach ($keyval as $kv) {
list($val1, $val2, $valn) = $kv;
}
No, but there are many ways to do this, e.g:
reset($tags_latest);
foreach ($bookmarks_latest as $bookmark){
$tags = current($tags_latest); next($tags_latest);
// here you can use $bookmark and $tags
}
No. No, it is not.
You'll have to manually write out a loop that uses indexes or internal pointers to traverse both arrays at the same time.
Yes, for completeness:
foreach (array_combine($bookmarks_latest, $tags_latest) as $bookm=>$tag)
That would be the native way to get what you want. But it only works if both input arrays have the exact same length, obviously.
(Using a separate iteration key is the more common approach however.)
I have a PHP script which reads a large CSV and performs certain actions, but only if the "username" field is unique. The CSV is used in more than one script, so changing the input from the CSV to only contain unique usernames is not an option.
The very basic program flow (which I'm wondering about) goes like this:
$allUsernames = array();
while($row = fgetcsv($fp)) {
$username = $row[0];
if (in_array($username, $allUsernames)) continue;
$allUsernames[] = $username;
// process this row
}
Since this CSV could actually be quite large, it's that in_array bit which has got me thinking. The most ideal situation when searching through an array for a member is if it is already sorted, so how would you build up an array from scratch, keeping it in order? Once it is in order, would there be a more efficient way to search it than using in_array(), considering that it probably doesn't know the array is sorted?
Not keeping the array in order, but how about this kind of optimization? I'm guessing isset() for an array key should be faster than in_array() search.
$allUsernames = array();
while($row = fgetcsv($fp)) {
$username = $row[0];
if (isset($allUsernames[$username])) {
continue;
} else {
$allUsernames[$username] = true;
// do stuff
}
}
The way to build up an array from scratch in sorted order is an insertion sort. In PHP-ish pseudocode:
$list = []
for ($element in $elems_to_insert) {
$index = binary_search($element, $list);
insert_into_list($element, $list, $index);
}
Although, it might actually turn out to be faster to just create the array in unsorted order and then use quicksort (PHP's builtin sort functions use quicksort)
And to find an element in a sorted list:
function binary_search($list, $element) {
$start = 0;
$end = count($list);
while ($end - $start > 1) {
$mid = ($start + $end) / 2;
if ($list[$mid] < $element){
$start = $mid;
}
else{
$end = $mid;
}
}
return $end;
}
With this implementation you'd have to test $list[$end] to see if it is the element you want, since if the element isn't in the array, this will find the point where it should be inserted. I did it that way so it'd be consistent with the previous code sample. If you want, you could check $list[$end] === $element in the function itself.
The array type in php is an ordered map (php array type). If you pass in either ints or strings as keys, you will have an ordered map...
Please review item #6 in the above link.
in_array() does not benefit from having a sorted array. PHP just walks along the whole array as if it were a linked list.