Related
I'm sure this is an extremely obvious question, and that there's a function that does exactly this, but I can't seem to find it. In PHP, I'd like to know if my array has duplicates in it, as efficiently as possible. I don't want to remove them like array_unique does, and I don't particularly want to run array_unique and compare it to the original array to see if they're the same, as this seems very inefficient. As far as performance is concerned, the "expected condition" is that the array has no duplicates.
I'd just like to be able to do something like
if (no_dupes($array))
// this deals with arrays without duplicates
else
// this deals with arrays with duplicates
Is there any obvious function I'm not thinking of?
How to detect duplicate values in PHP array?
has the right title, and is a very similar question, however if you actually read the question, he's looking for array_count_values.
I know you are not after array_unique(). However, you will not find a magical obvious function nor will writing one be faster than making use of the native functions.
I propose:
function array_has_dupes($array) {
// streamline per #Felix
return count($array) !== count(array_unique($array));
}
Adjust the second parameter of array_unique() to meet your comparison needs.
Performance-Optimized Solution
If you care about performance and micro-optimizations, check this one-liner:
function no_dupes(array $input_array) {
return count($input_array) === count(array_flip($input_array));
}
Description:
Function compares number of array elements in $input_array with array_flip'ed elements. Values become keys and guess what - keys must be unique in associative arrays so not unique values are lost and final number of elements is lower than original.
Warning:
As noted in the manual, array keys can be only type of int or string so this is what you must have in original array values to compare, otherwise PHP will start casting with unexpected results. See https://3v4l.org/7bRXI for an example of this fringe-case failure mode.
Proof for an array with 10 million records:
The top-voted solution by Jason McCreary: 14.187316179276s 🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌
The accepted solution by Mike Sherov: 2.0736091136932s 🐌🐌
This answer's solution: 0.14155888557434s 🐌/10
Test case:
<?php
$elements = array_merge(range(1,10000000),[1]);
$time = microtime(true);
accepted_solution($elements);
echo 'Accepted solution: ', (microtime(true) - $time), 's', PHP_EOL;
$time = microtime(true);
most_voted_solution($elements);
echo 'Most voted solution: ', (microtime(true) - $time), 's', PHP_EOL;
$time = microtime(true);
this_answer_solution($elements);
echo 'This answer solution: ', (microtime(true) - $time), 's', PHP_EOL;
function accepted_solution($array){
$dupe_array = array();
foreach($array as $val){
// sorry, but I had to add below line to remove millions of notices
if(!isset($dupe_array[$val])){$dupe_array[$val]=0;}
if(++$dupe_array[$val] > 1){
return true;
}
}
return false;
}
function most_voted_solution($array) {
return count($array) !== count(array_unique($array));
}
function this_answer_solution(array $input_array) {
return count($input_array) === count(array_flip($input_array));
}
Notice that accepted solution might be faster in certain condition when not unique values are near the beginning of huge array.
You can do:
function has_dupes($array) {
$dupe_array = array();
foreach ($array as $val) {
if (++$dupe_array[$val] > 1) {
return true;
}
}
return false;
}
$hasDuplicates = count($array) > count(array_unique($array));
Will be true if duplicates, or false if no duplicates.
Here's my take on this… after some benchmarking, I found this to be the fastest method for this.
function has_duplicates( $array ) {
return count( array_keys( array_flip( $array ) ) ) !== count( $array );
}
…or depending on circumstances this could be marginally faster.
function has_duplicates( $array ) {
$array = array_count_values( $array );
rsort( $array );
return $array[0] > 1;
}
$duplicate = false;
if(count(array) != count(array_unique(array))){
$duplicate = true;
}
Keep it simple, silly! ;)
Simple OR logic...
function checkDuplicatesInArray($array){
$duplicates=FALSE;
foreach($array as $k=>$i){
if(!isset($value_{$i})){
$value_{$i}=TRUE;
}
else{
$duplicates|=TRUE;
}
}
return ($duplicates);
}
Regards!
To remove all the empty values from the comparison you can add array_diff()
if (count(array_unique(array_diff($array,array("")))) < count(array_diff($array,array(""))))
Reference taken from #AndreKR answer from here
Two ways to do it efficiently that I can think of:
inserting all the values into some sort of hashtable and checking whether the value you're inserting is already in it(expected O(n) time and O(n) space)
sorting the array and then checking whether adjacent cells are equal( O(nlogn) time and O(1) or O(n) space depending on the sorting algorithm)
stormdrain's solution would probably be O(n^2), as would any solution which involves scanning the array for each element searching for a duplicate
Find this useful solution
function get_duplicates( $array ) {
return array_unique( array_diff_assoc( $array, array_unique( $array ) ) );
}
After that count result if greater than 0 than duplicates else unique.
I'm using this:
if(count($array)==count(array_count_values($array))){
echo("all values are unique");
}else{
echo("there's dupe values");
}
I don't know if it's the fastest but works pretty good so far
One more solution from me, this is related to performance improvement
$array_count_values = array_count_values($array);
if(is_array($array_count_values) && count($array_count_values)>0)
{
foreach ($array_count_values as $key => $value)
{
if($value>1)
{
// duplicate values found here, write code to handle duplicate values
}
}
}
As you specifically said you didn't want to use array_unique I'm going to ignore the other answers despite the fact they're probably better.
Why don't you use array_count_values() and then check if the resulting array has any value greater than 1?
Php has an function to count the occurrences in the array http://www.php.net/manual/en/function.array-count-values.php
You can do it like that way also:
This will return true if unique else return false.
$nofollow = (count($modelIdArr) !== count(array_unique($modelIdArr))) ? true : false;
The simple solution but quite faster.
$elements = array_merge(range(1,10000000),[1]);
function unique_val_inArray($arr) {
$count = count($arr);
foreach ($arr as $i_1 => $value) {
for($i_2 = $i_1 + 1; $i_2 < $count; $i_2++) {
if($arr[$i_2] === $arr[$i_1]){
return false;
}
}
}
return true;
}
$time = microtime(true);
unique_val_inArray($elements);
echo 'This solution: ', (microtime(true) - $time), 's', PHP_EOL;
Speed - [0.71]!
function hasDuplicate($array){
$d = array();
foreach($array as $elements) {
if(!isset($d[$elements])){
$d[$elements] = 1;
}else{
return true;
}
}
return false;
}
I can not figure out how to print all $_POST array items (ending in successive numbers) if one or more numbers do not exist. Not sure how to explain this... For example..
$i = 1;
while( isset($options['item_code'.$i]) )
{
echo $options['item_code'.$i];
$i++;
}
This code works fine as long as the numbers continue to exist in order...
item_code, item_code1, item_code2, item_code3, etc...
But once a number is removed, the if statement stops and the rest of the values are not printed. For example...
item_code, item_code1, item_code3, etc...
Will stop at "item_code1" because item_code2 does not exist.
I've tried solutions given to similar questions here on stackoverflow but they either do not work, do the same thing, or create a continuous loop.
I would appreciate any help that someone can give me here.
you are doing it in wrong way. Please update your code like this. replace $i<=4 with number of element you want to trace
$key = end(array_keys($options));
$dataa = explode('item_code',$key);
$count = $dataa[1];
$i = 1;
while( $i <= $count )
{
if(isset($options['item_code'.$i])){
echo $options['item_code'.$i];
}
$i++;
}
I guess it can be done with an array_filter and strpos functions:
<?php
$codes = array_filter($options, function ($key) {
return strpos($key, 'item_code') === 0;
}, ARRAY_FILTER_USE_KEY);
foreach ($codes as $code) {
echo $code . PHP_EOL;
}
Instead of while use foreach like
foreach($options as $option){
echo $value;
}
I am trying to learn php, and I am playing around with while loops. I was wondering how to print out a specific number in an array in php. Fx:
$a = [1,3,5,7,9,11,13];
$s = 3;
while($a == 3) {
echo $s.' is in the row';
$a++;
}
In this example I would like to run through the $a and see if 3 exist there. If it does it has to echo '3 is in the row' I tried to make a while loop, but it is not correct. Can anyone see what I am doing wrong? Just to say it, I think it is very wrong, but I don't know how to solve it, if I have to use the while loop?
Best Regards
Mads
Your while condition reads: "While the value of $a equals 3", but $a is an array, so its value can't ever be 3. The loop will never be executed. In PHP, we would write:
if (in_array($s, $a))
echo $s, ' was found in the array';
Or, if you insist on writing loops:
foreach ($a as $key => $value)
{
if ($value == $s)
{
echo $s, ' was found at offset ', $key;
break;//end terminate loop
}
}
Of course, you could also write:
for ($i=0, $j=count($a);$i<$j;++$j)
{
if ($a[$i] == $s)
{//you could move this condition to the loop itself, even
echo $s, ' found in array at offset ', $i;
break;
}
}
You can, if you want use a while loop, too, but that wouldn't be the best choice for your particular case. Just read through the manual on php.net. There are many, many array_* functions available, and there are many ways to iterate over your data.
Another worry is your using the array name as a sort-of C-style pointer: $a++; in C, an pointer can be incremented to set it to point to the next value in an array (if the new memory address is valid, and the pointer is valid, and all of the other things you have to worry about in C). PHP does not work this way. An array isn't really an array: it's a hash map. incrementing an array, therefore, is pointless and most likely to be a bug. The for loop is the closest you can get to traversing an array using the ++ operator.
You're looking for in_array. This checks if a value exists in an array, in the form of:
in_array ( mixed $needle , array $haystack )
So, in your case, you'd want to do:
$a = [1,3,5,7,9,11,13];
$s = 3;
if (in_array($s, $a)) {
echo $s.' is in the row';
}
foreach($a as $b) {
if($b == 3)
echo $b.' is in the row';
}
Modify slightly your code changing while condition:
$a = array(1,3,5,7,9,11,13);
$s = 3;
$counter = 0;
while($counter < count($a)) {
if ( $a[$counter] == $s )
echo $s.' is in the row';
$counter++;
}
Added counter to iterate through while loop until end of array.
count() method returns number of items in array.
This solution prints all occurences of your number.
To have better code, change names of variables:
$numbers = array(1,3,5,7,9,11,13);
$target = 3;
$counter = 0;
while($counter < count($numbers)) {
if ( $numbers[$counter] == $target )
echo $target.' is in the row';
$counter++;
}
There are two ways to do it,
First, you can loop through all items in the array using a foreach() loop.
That way, you can go through them all and if you have multiple conditions, it makes your code a bit more readable.
And example of that loop is like this:
foreach($array as $array_item) {
if($array_item === 3) {
echo "3 is in the array";
}
}
The alternative is to use a built in function to find if something is in the array. THis is probably much faster, though I haven't benchmarked the difference.
if(in_array(3, $array)) {
echo "3 is in the array";
}
you can use
array_search ,in_array , and forearch or for loops to itertate through the array.
For learning purposes
$a = [1,3,5,7,9,11,13];
$s = 3;
for($i=0;$i<count($a);$i++)
{
if($a[$i]==$s){
echo $s.' is in the row';
}
}
of course in real life
if (in_array(3, $a)) {
// Do something
}
would be better;
<?php
$a = [1,3,5,7,9,11,13];
$s = 3;
for($a=0;$a < 20; $a++)
{
while($a == 3) {
echo $s.' is in the row';
//$a++;
}
}
?>
I'm getting a very weird results when trying to loop through a comma delimited list in PHP.
It sometimes only outputs a few of them and there seems no logical reason to why it doesn't loop through all of them, and I can't for the life of me figure out what's actually causing it.
My code is:
//pids = &pids=1,2,3,6,7,9
$pids = $_GET['pids'];
$photoIdArray = explode(",", $pids);
for($i = 0; $i <= count($photoIdArray); $i++) {
foreach($photoIdArray as $j){
if($i == $j){
echo "{$j}";
}
}
}
// result = 1236
This is just for testing so there is im not checking the inputs to prevent exploits and what not at the moment.
Any help would be appreciated.
Thanks!
Combining 2 loop for and foreach is overkill for something like this
Try using only foreach
$pids = "1,2,3,6,7,9";
$photoIdArray = explode(",", $pids);
foreach($photoIdArray as $value)
{
echo $value;
}
Output
123679
It is because you are looping through your values and check if $i is the same as the value. You should check
if ($photoIdArray[$i] == $j) {
instead of
if ($i == $j) {
This is the reason it didn't work, but you should still use Baba's method.
I agree with Dusan, Baba & Co., but to answer the actual question:
Nothing weird happens here. i loops from 0 to 6 (though the array has only indices 0..5), and you compare i with the VALUES of the array, which range from 1 to 9. Of course, only the values 1 to 6 are matched, because i never exceeds 6.
EDIT: Asad and Sietse were faster.
I'm sure this is an extremely obvious question, and that there's a function that does exactly this, but I can't seem to find it. In PHP, I'd like to know if my array has duplicates in it, as efficiently as possible. I don't want to remove them like array_unique does, and I don't particularly want to run array_unique and compare it to the original array to see if they're the same, as this seems very inefficient. As far as performance is concerned, the "expected condition" is that the array has no duplicates.
I'd just like to be able to do something like
if (no_dupes($array))
// this deals with arrays without duplicates
else
// this deals with arrays with duplicates
Is there any obvious function I'm not thinking of?
How to detect duplicate values in PHP array?
has the right title, and is a very similar question, however if you actually read the question, he's looking for array_count_values.
I know you are not after array_unique(). However, you will not find a magical obvious function nor will writing one be faster than making use of the native functions.
I propose:
function array_has_dupes($array) {
// streamline per #Felix
return count($array) !== count(array_unique($array));
}
Adjust the second parameter of array_unique() to meet your comparison needs.
Performance-Optimized Solution
If you care about performance and micro-optimizations, check this one-liner:
function no_dupes(array $input_array) {
return count($input_array) === count(array_flip($input_array));
}
Description:
Function compares number of array elements in $input_array with array_flip'ed elements. Values become keys and guess what - keys must be unique in associative arrays so not unique values are lost and final number of elements is lower than original.
Warning:
As noted in the manual, array keys can be only type of int or string so this is what you must have in original array values to compare, otherwise PHP will start casting with unexpected results. See https://3v4l.org/7bRXI for an example of this fringe-case failure mode.
Proof for an array with 10 million records:
The top-voted solution by Jason McCreary: 14.187316179276s 🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌🐌
The accepted solution by Mike Sherov: 2.0736091136932s 🐌🐌
This answer's solution: 0.14155888557434s 🐌/10
Test case:
<?php
$elements = array_merge(range(1,10000000),[1]);
$time = microtime(true);
accepted_solution($elements);
echo 'Accepted solution: ', (microtime(true) - $time), 's', PHP_EOL;
$time = microtime(true);
most_voted_solution($elements);
echo 'Most voted solution: ', (microtime(true) - $time), 's', PHP_EOL;
$time = microtime(true);
this_answer_solution($elements);
echo 'This answer solution: ', (microtime(true) - $time), 's', PHP_EOL;
function accepted_solution($array){
$dupe_array = array();
foreach($array as $val){
// sorry, but I had to add below line to remove millions of notices
if(!isset($dupe_array[$val])){$dupe_array[$val]=0;}
if(++$dupe_array[$val] > 1){
return true;
}
}
return false;
}
function most_voted_solution($array) {
return count($array) !== count(array_unique($array));
}
function this_answer_solution(array $input_array) {
return count($input_array) === count(array_flip($input_array));
}
Notice that accepted solution might be faster in certain condition when not unique values are near the beginning of huge array.
You can do:
function has_dupes($array) {
$dupe_array = array();
foreach ($array as $val) {
if (++$dupe_array[$val] > 1) {
return true;
}
}
return false;
}
$hasDuplicates = count($array) > count(array_unique($array));
Will be true if duplicates, or false if no duplicates.
Here's my take on this… after some benchmarking, I found this to be the fastest method for this.
function has_duplicates( $array ) {
return count( array_keys( array_flip( $array ) ) ) !== count( $array );
}
…or depending on circumstances this could be marginally faster.
function has_duplicates( $array ) {
$array = array_count_values( $array );
rsort( $array );
return $array[0] > 1;
}
$duplicate = false;
if(count(array) != count(array_unique(array))){
$duplicate = true;
}
Keep it simple, silly! ;)
Simple OR logic...
function checkDuplicatesInArray($array){
$duplicates=FALSE;
foreach($array as $k=>$i){
if(!isset($value_{$i})){
$value_{$i}=TRUE;
}
else{
$duplicates|=TRUE;
}
}
return ($duplicates);
}
Regards!
To remove all the empty values from the comparison you can add array_diff()
if (count(array_unique(array_diff($array,array("")))) < count(array_diff($array,array(""))))
Reference taken from #AndreKR answer from here
Two ways to do it efficiently that I can think of:
inserting all the values into some sort of hashtable and checking whether the value you're inserting is already in it(expected O(n) time and O(n) space)
sorting the array and then checking whether adjacent cells are equal( O(nlogn) time and O(1) or O(n) space depending on the sorting algorithm)
stormdrain's solution would probably be O(n^2), as would any solution which involves scanning the array for each element searching for a duplicate
Find this useful solution
function get_duplicates( $array ) {
return array_unique( array_diff_assoc( $array, array_unique( $array ) ) );
}
After that count result if greater than 0 than duplicates else unique.
I'm using this:
if(count($array)==count(array_count_values($array))){
echo("all values are unique");
}else{
echo("there's dupe values");
}
I don't know if it's the fastest but works pretty good so far
One more solution from me, this is related to performance improvement
$array_count_values = array_count_values($array);
if(is_array($array_count_values) && count($array_count_values)>0)
{
foreach ($array_count_values as $key => $value)
{
if($value>1)
{
// duplicate values found here, write code to handle duplicate values
}
}
}
As you specifically said you didn't want to use array_unique I'm going to ignore the other answers despite the fact they're probably better.
Why don't you use array_count_values() and then check if the resulting array has any value greater than 1?
Php has an function to count the occurrences in the array http://www.php.net/manual/en/function.array-count-values.php
You can do it like that way also:
This will return true if unique else return false.
$nofollow = (count($modelIdArr) !== count(array_unique($modelIdArr))) ? true : false;
The simple solution but quite faster.
$elements = array_merge(range(1,10000000),[1]);
function unique_val_inArray($arr) {
$count = count($arr);
foreach ($arr as $i_1 => $value) {
for($i_2 = $i_1 + 1; $i_2 < $count; $i_2++) {
if($arr[$i_2] === $arr[$i_1]){
return false;
}
}
}
return true;
}
$time = microtime(true);
unique_val_inArray($elements);
echo 'This solution: ', (microtime(true) - $time), 's', PHP_EOL;
Speed - [0.71]!
function hasDuplicate($array){
$d = array();
foreach($array as $elements) {
if(!isset($d[$elements])){
$d[$elements] = 1;
}else{
return true;
}
}
return false;
}