Split 5 or 6 character number before fourth-last number - php

Question

I get POST request date strings in the format of mY (no leading zeros on the month), so there's no delimiting character to split on.
Examples: 122019 or 62019
I need to separate the five or six digit string into a one or two digit month and a four digit year.
Eg1 : 122019
$a[0] = 12;
$a[1] = 2019
Eg2 : 62021
$a[0] = 6;
$a[1] = 2021

Answer 1

I don't know about this date format, especially about how you use an integer as a date. But let's consider that it's on purpose, the year is always gonna be 4 character, so you can just get the year by taking the last 4 char and use the rest as the month.
Using substr() see PHP.NET Substr
Return part of a string
And you can specify the start and length of the part you want to get, or using - to get character starting from the end of the string.
$weirdDate = 122019;
//takes the last 4 character
$year = substr($weirdDate , -4);
//takes the string from the beginning to 4 char before the end
$month = substr($weirdDate , 0,strlen($weirdDate)-4);
echo $year;
echo $month;
Again, it seems like a weird way to get a month/year date, but i'm answering based on the assumption that a year is gonna be 4 char long.
If it's not, you can't really split the number since the month part can be 1 or 2 char long.
09-2019 would be 92019
11-2019 would be 112019

Answer 2

A simple use of the substr() function will do this nicely
$in = '122019';
$year = substr($in,-4);
$month = substr($in,0, strlen($in)-4);
echo $year . ' month ' . $month;
$a[] = $month;
$a[] = $year;
RESULT
2019 month 12
array (
[0] => 12
[1] => 2019
)
Or if we use $in = '62019';
The RESULT would be
2019 month 6
array (
[0] => 6
[1] => 2019
)
Reference 'substr()`

Answer 3

You could also use substr with strpos. With substr(), you could first get the year by providing a negative offset to start capturing from back of the string as the year is going to be 4 digits. Then, you could use strpos() to find the index of the year and use this as the ending index to get the month.
That being said, best way to deal with this data is to either have a proper date format or better to have a JSON string with proper keys for days, month and year along with date.
Code:
<?php
$str = '122019';
$year = substr($str,-4);
$month = substr($str,0,strpos($str,$year));
echo $month," ",$year;

Answer 4

I have one another solution to use str_replace() with substr() like:
<?php
$string = "122019";
$year = substr($string, -4);
$date = str_replace($year, "", $string);
$myArray = array($date,$year); // convert into an array
echo "<pre>";
print_r($myArray);
?>
Desired Output:
Array
(
[0] => 12
[1] => 2019
)
Side Note: This will only work, if your year based on last 4 characters and other then these 4 characters must be date, as you mentioned in your question.

Answer 5

To accomplish this feat with two function calls, use negative parameters with substr() calls.
There is no reason to call strlen(), strpos(), or str_replace().
For a single call technique, use preg_split() with a lookahead pattern to ensure that no characters are consumed while exploding.
Codes: (Demo)
$mY = '62021';
var_export([
substr($mY, 0, -4), // month
substr($mY, -4) // year
]);
echo "\n---\n";
var_export(
preg_split('/(?=\d{4}$)/', $mY)
);