Print a sequence of numbers in PHP with the correct (+/-) sign

Question

I need to print some numbers in a sequence with + and - between them. However, I don't know beforehand which number is going to be positive and which is going to be negative. Currently, I echo them like this:

echo "$a + $b + $c + $d + $e + $f";

Let's say the values of $a to $f are all positive. I will get something like: 5 + 10 + 12 + 18 + 9 + 7.

However, if some of the values are negative, I will get something like 5 + -10 + 12 + -18 + 9 + - 7. The ideal output in this case would have been 5 - 10 + 12 - 18 + 9 - 7.

Please not that I don't want to calculate the final result of addition or subtraction. I just want to print it all on the webpage with correct signs.

I could do so by writing 6 nested if() blocks but that seems like a lot of work and doing it every time will be error prone. Is there anything clever that I can do to output the right sign.

What should it look like if the first number is negative? – Phil Jul 11 '18 at 06:13 — Phil, Jul 11 '18 at 06:13

score 2 · Accepted Answer · answered Jul 11 '18 at 06:19

The easiest way would be to correct the operator appearance in the final string:

$s = '5 + -10 + 12 + -18 + 9 + - 7'; // result of interpolation or concatenation
$s = str_replace('+ -', '- ', $s);
// => "5 - 10 + 12 - 18 + 9 -  7"

If this is possible for you, this is as fast as it gets -- no looping (in php), no treating each number one at a time with a conditional. If you loop anyway, I'd recommend @Phils suggestion with array_reduce -- functional style php -- adapted to your needs.

Thanks @Tom. This seems to be the most efficient and easiest way of changing signs. :) — iKnowNothing, Jul 11 '18 at 06:42

score 1 · Answer 2 · answered Jul 11 '18 at 05:55

1

Need to check for each variable manually like this:

echo "$a " . ($b < 0 ? " - " . abs($b) : " + $b") . ($c < 0 ? " - " . abs($c) : " + $c") . ($d < 0 ? " - " . abs($d) : " + $d") . ($e < 0 ? " - " . abs($e) : " + $e") . ($f < 0 ? " - " . abs($f) : " + $f");

answered Jul 11 '18 at 05:55

Lovepreet Singh

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Thanks @Lovepreet. I was looking for some other way that will keep the original echo statement short and simple. Your way is still much better than using 6 different `if()` blocks. :) – iKnowNothing Jul 11 '18 at 05:57

nageen nayak · Answer 3 · 2018-07-11T05:59:00.447

1

you can use php sprintf function.

function formatNum($num){
    return sprintf("%+d",$num);
}

or

function formatNum($num) {
  $num = (int) $num; // or (float) if you'd rather
  return (($num >= 0) ? '+' : '-') . $num; // implicit cast back to string
}

for more detail please read it :- http://php.net/manual/en/function.sprintf.php

edited Jul 11 '18 at 05:59

answered Jul 11 '18 at 05:57

nageen nayak

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SO reference: https://stackoverflow.com/questions/2682397/how-to-prefix-a-positive-number-with-plus-sign-in-php – e_i_pi Jul 11 '18 at 05:58

score 1 · Answer 4 · answered Jul 11 '18 at 05:59

1

try this

$a = 10;

$b=-20;

$text = $a." ".$b;

$text= str_replace(" ", "+", $text);

echo $text;

OUTPUT

10+-20

answered Jul 11 '18 at 05:59

Chirag

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2
12

Phil · Answer 5 · 2018-07-11T06:13:15.747

1

Put the numbers in an array and use array_reduce to create the string

$numbers = [5, -10, 12, -18, 9, -7];
$first = array_shift($numbers);

echo array_reduce($numbers, function($str, $num) {
    return $str . sprintf(' %s %d', $num < 0 ? '-' : '+', abs($num)); 
}, $first);

Demo ~ https://eval.in/1034635

This way you can handle an arbitrary amount of numbers without duplicating logic everywhere.

edited Jul 11 '18 at 06:13

answered Jul 11 '18 at 06:06

Phil

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Print a sequence of numbers in PHP with the correct (+/-) sign

5 Answers5