Summing string in php, converted to integer - php

Question

Trying to use a simple "versioning" system for some hashes, I do the following:
$last_version = '009';
$increment = '001';
$result = $last_version + $increment;
var_dump($result);
I would expect: string(010) but I get int(10) and before I jump into if's and str-pad, I was wondering if there's any other way of conserving the desired format?

Answer 1

Using + automatically casts the variables into the appropriate number type (in this case an int, however different string formats can be casted to float).
If you want to keep the desired 0 left-padding, you can use sprintf() to format the result, as such:
$result = sprintf('%03d', $last_version + $increment);
The format specifier %03d specifies that you want an integer-string (d) with a length of 3 left-padded with the character 0.
More information about PHP's Type Juggling logic can be found in the PHP Documentation: Type Juggling

Answer 2

$last_version = '009';
$increment = '001';
$result = $last_version + $increment;
$result = (string) $result ;
var_dump($result) ;
When you try to perform math operations with strings, they are cast to approprite type. In this case to int. But you can cast integer back to string in the above example.

Answer 3

You cannot add strings (it's as simple as that). That's why PHP implicitly converts both strings to integers (this is called dynamic typing).
To format your number, you could to the following:
$last_version = '009';
$increment = '001';
$result = $last_version + $increment; // = 10
$result = sprintf("%03d", $result) // = "010"

Answer 4

When you use +, PHP will automatically cast the string to integers, thus the int(10 result you are seeing. You will not be able to add strings in this manner. So you best best would be to just keep the version as integer ans string pad like this:
$last_version = 9;
$increment = 1;
$pad_length = 3;
$pad_string = '0';
$result = $last_version + increment; // or simply $last_version++; if increment will always be 1
$string_result = str_pad((string)$result, $pad_length, $pad_string, STR_PAD_LEFT);