I want to convert as below via preg_replace - preg-replace

Question

I want to convert as below via preg_replace.
How can i know answer??
preg_replace($pattern, "$2/$1", "One001Two111Three");
result> Three/Two111/One001

Answer 1

You'd better use preg_split, it's much more simple than preg_replace and it works with any number of elements:
$str = "One001Two111Three";
$res = implode('/', array_reverse(preg_split('/(?<=\d)(?=[A-Z])/', $str)));
echo $res,"\n";
output:
Three/Two111/One001
The regex /(?<=\d)(?=[A-Z])/ splits on boundary between a digit and a capital letter, array_reverse reverse the order of the array given by preg_split, then the elements of reversed array are joined by implode with a /

Answer 2

$string = "One001Two111Three";
$result = preg_replace('/^(.*?\d+)(.*?\d+)(.*?)$/im', '$3/$2/$1', $string );
echo $result;
RESULT: Three/Two111/One001
DEMO
EXPLANATION:
^(.*?\d+)(.*?\d+)(.*?)$
-----------------------
Options: Case insensitive; Exact spacing; Dot doesn't match line breaks; ^$ match at line breaks; Greedy quantifiers; Regex syntax only
Assert position at the beginning of a line (at beginning of the string or after a line break character) (line feed) «^»
Match the regex below and capture its match into backreference number 1 «(.*?\d+)»
Match any single character that is NOT a line break character (line feed) «.*?»
Between zero and unlimited times, as few times as possible, expanding as needed (lazy) «*?»
Match a single character that is a “digit” (any decimal number in any Unicode script) «\d+»
Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match the regex below and capture its match into backreference number 2 «(.*?\d+)»
Match any single character that is NOT a line break character (line feed) «.*?»
Between zero and unlimited times, as few times as possible, expanding as needed (lazy) «*?»
Match a single character that is a “digit” (any decimal number in any Unicode script) «\d+»
Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
Match the regex below and capture its match into backreference number 3 «(.*?)»
Match any single character that is NOT a line break character (line feed) «.*?»
Between zero and unlimited times, as few times as possible, expanding as needed (lazy) «*?»
Assert position at the end of a line (at the end of the string or before a line break character) (line feed) «$»
$3/$2/$1
Insert the text that was last matched by capturing group number 3 «$3»
Insert the character “/” literally «/»
Insert the text that was last matched by capturing group number 2 «$2»
Insert the character “/” literally «/»
Insert the text that was last matched by capturing group number 1 «$1»