PHP: How to decrement a string function by 1?

Question

I'm using PHP to access an external API.

When a call a particular API method, it returns a number one higher than I want to display.

However, the API is returning the integer as a string and not an integer.

Question: How can I decrement the returned string by 1 since it's not an integer

Essentially, I want to do the follow pseudo-code (that doesn't work):

echo external_api() -1; // problem is, this returns "X -1" where "X" is an integer but returned as a strong

Answer 1

Cast it with (int) or use intval() to convert it to an integer first:

echo ((int) external_api()) - 1;

or

echo intval(external_api()) - 1;

Casting is generally the fastest.

Answer 2

You can cast the return value as integer :

echo ((int) external_api()) - 1; 

** EDIT **

This is the code that I ran

function external_api() {
    return "100";
}

echo ((int) external_api()) - 1; 

and the output is 99. If this doesn't work for you, then the function is not returning a correct value. Otherwise, please elaborate because it doesn't make any sense.

Moreover, as deceze pointed out, even without casting, PHP is smart enough to do it already on math operators :

echo external_api() - 1; 

will also output 99 so obviously there is something going on in that mysterious function because the problem is not where you say it is.

BTW : the result of "2" -1; can never be "2 -1" because - is not even a string operator. The only string operator in PHP is . for concatenation: "2" + 1 = 3; where "2" . 1 = "21"

Answer 3

try echo intval(external_api())-1 or if some higher no or other data type floatval too

Answer 4

If the function is returning a string, then your code should actually work. You could try casting the value to an integer though:

echo (int)external_api() - 1;

EDIT

It sounds like you might need to sanitize your data using preg_replace before decrementing it. Try this:

echo preg_replace('/[^0-9]/', '', external_api()) - 1;

Answer 5

@Yanick Rochon

Assume external_api() = 9

So when I do var_dump(external_api()); it returns 9NULL

Any idea why?

Answer 6

The external_api() function echoes the integer (9) and returns NULL. Thus, when you attempt to subtract from it, you get something like the following:

function external_api() {echo "9";}
echo external_api() - 1;

...which would produce 9-1.

Mystery solved.

Now, to fix it. Supposing you can't change the external api...

ob_start();
external_api();
$output = ob_get_clean();
echo ((int)$output) - 1;

Next time, though, post everything, so we're not scratching our heads for an extended period of time.