Replace one string in an array but leave others untouched in php - php

Question

Say I have an array of strings like this:
$in_arr = ['a', 'a', 'b', 'b', 'a', 'b', 'b', 'a', 'a', 'b'];
I would like an efficient way to merge all a's into a single value but leave the b's untouched so the result will be:
['a', 'b', 'b', 'a', 'b', 'b', 'a', 'b']

Answer 1

This is a possible solution:
<?php
define('ASPECT', 'a');
$input = ['a', 'a', 'b', 'b', 'a', 'b', 'b', 'a', 'a', 'b'];
$output = [];
array_walk($input, function($entry) use (&$output) {
if (($entry != ASPECT) || (end($output) != ASPECT)) {
$output[] = $entry;
}
});
print_r($output);
The output obviously is:
Array
(
[0] => a
[1] => b
[2] => b
[3] => a
[4] => b
[5] => b
[6] => a
[7] => b
)

Answer 2

With array_reduce:
$res = array_reduce($arr, function ($c, $i) {
if ( $i!='a' || end($c)!='a' )
$c[] = $i;
return $c;
}, []);

Answer 3

You could iterate through the list and only add strings to a new list if they're not your key string or if they are different from the previous string, something like this:
$in_arr = ['a', 'a', 'b', 'b', 'a', 'b', 'b', 'a', 'a', 'b'];
$new_arr = [];
$last = '';
$key = 'a';
foreach ($in_arr as $item) {
if ($key == $item and $item == $last) {
continue;
}
$last = $item;
array_push($new_arr, $item);
}
echo "[";
foreach( $new_arr as $value ){
echo $value.", ";
}
echo "]";
produces
[a, b, b, a, b, b, a, b, ]
Edit: PHP sandbox

Answer 4

You Require code :
<?php
$in_arr = array('a', 'a', 'b', 'b', 'a', 'b', 'b', 'a', 'a', 'b');
$last_temp = '';
for($i=0;$i<count($in_arr);$i++)
{
if($last_temp == $in_arr[$i] && $in_arr[$i]=='a')
{
unset($in_arr[$i]);
$in_arr = array_values($in_arr);
}
else
{
$last_temp = $in_arr[$i];
}
}
echo json_encode($in_arr);
Output :
["a","b","b","a","b","b","a","b"]