Dynamic explosion with specific character - php

Question

I am trying to extract a string in php and convert them to comma separated strings
Here are some sample string I am working with and the results I need:
input :
G1_C2_S3_T5 or G4_C5_S4_T7_I6_H3
Result must be :
G1,G1_C2,G1_C2_S3,G1_C2_S3_T5
or
G4,G4_C5,G4_C5_S4,G4_C5_S4_T7,G4_C5_S4_T7_I6,G4_C5_S4_T7_I6_H3
Input length can be dynamic for comma separation
Is this correct :
$arr = explode("_", $string, 2);
$first = $arr[0];
How can i do that in php?

Answer 1

Something like this should work, $string is the string you are working with
//explode by underscore
$parts = explode('_', $string);
$c = [];
//do until nothing else to pop from array
while (!empty($parts)) {
$c[] = implode('_', $parts);
//will pop element from end of array
array_pop($parts);
}
//reverse
$c = array_reverse($c);
//glue it with comma
echo implode(',', $c);

Answer 2

You should notice that the number of underscore-separated values in your initial string e.g. G4_C5_S4_T7_I6_H3 (6) is equal to the number of comma-separated values in your desired string e.g. G4,G4_C5,G4_C5_S4,G4_C5_S4_T7,G4_C5_S4_T7_I6,G4_C5_S4_T7_I6_H3 (6). So we'll use this number in our first loop $end = count($parts).
$str = "G4_C5_S4_T7_I6_H3";
$newstr = '';
$parts = explode('_', $str);
$comma = '';
for ($i = 0, $end = count($parts); $i < $end; $i++) {
$newstr .= $comma;
$underscore = '';
// build underscore-separated value
// index i is used to indicate up which value to stop at for each iteration
for ($j = 0; $j <= $i; $j++) {
$newstr .= $underscore . $parts[$j];
// set underscore after the first iteration of the loop
$underscore = '_';
}
// set comma after the first iteration of the loop
$comma = ',';
}
echo $newstr; // G4,G4_C5,G4_C5_S4,G4_C5_S4_T7,G4_C5_S4_T7_I6,G4_C5_S4_T7_I6_H3

Answer 3

The explosion is easy:
$parts = explode('_', $string);
Now you get a $parts array like [ 'G1', 'C2', 'S3', 'T5' ].
You want to convert this to an array so that each item is the concatenation of that item and every other item before it:
$prev = [ ];
array_walk(
$parts,
function(&$value) use (&$prev) {
$prev[] = $value;
$value = implode('_', $prev);
}
);
Now $parts holds the elements:
print implode(', ', $parts);
yields
G1, G1_C2, G1_C2_S3, G1_C2_S3_T5