How to add string into array in PHP? - php

Question

I have these for loop to determine consecutive number. What I achieve so far is to print the output in string.
$arr = [1,2,3,6,11,5,4,8,9,3];
for($start=0; $start<=count($arr); $start++){
for($end=$start+1; $end<=count($arr); $end++){
$total = $arr[$end] - $arr[$start];
if($total == 1){
echo 'Number is '.$arr[$start].','.$arr[$end].'<br/>';
} else {
echo '';
}
$arr[$start++];
}
}
My goal is to add the output into array.
I tried to use multidimensional array but no output display.
$arr = [1,2,3,6,11,5,4,8,9,3];
$arr3 = [];
for($start=0; $start<=count($arr); $start++){
for($end=$start+1; $end<=count($arr); $end++){
$total = $arr[$end] - $arr[$start];
if($total == 1){
$arr2 = array();
$arr2[] = $arr[$start].','.$arr[$end].'';
$arr3[] = $arr2;
} else {
}
$arr[$start++];
}
}
echo '<pre>';
print_r($arr3);
echo '</pre>';
exit;
Appreciate if someone can help me. Thanks.

Answer 1

you can simply use array functions, if sorting is important to you as #nice_dev said, you must sort your array before.
$arr = [1,2,3,6,11,5,4,8,9,3];
$cons = [] ;
while (array_key_last($arr) != key($arr)) {
if ((current($arr)+1) == next($arr)) {
prev($arr);
$cons[] = current($arr) . ',' . next($arr);
}
}
print_r($cons);
the output will be :
Array
(
[0] => 1,2
[1] => 2,3
[2] => 8,9
)

Answer 2

You can better sort() the input array first. This way, collecting all consecutive elements would get much simpler. If value at any index isn't +1 of the previous one, we add the $temp in our $results array and start a new $temp from this index.
Snippet:
<?php
$arr = [1,2,3,6,11,5,4,8,9,3];
$result = [];
sort($arr);
$temp = [];
for($i = 0; $i < count($arr); ++$i){
if($i > 0 && $arr[ $i ] !== $arr[$i - 1] + 1){
$result[] = implode(",", $temp);
$temp = [];
}
$temp[] = $arr[$i];
if($i === count($arr) - 1) $result[] = implode(",", $temp);
}
print_r($result);
Online Demo