Check negative value in php

I was wondering if there is any way to detect if a number is negative in PHP?

I have the following code:

$profitloss = $result->date_sold_price - $result->date_bought_price;

I need to find out if $profitloss is negative and if it is, I need to echo out that it is.

jozala

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asked May 26, 2011 at 7:44

BigJobbiesBigJobbies

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4

if ($profitloss < 0)
{
   echo "The profitloss is negative";
}

Edit: I feel like this was too simple an answer for the rep so here's something that you may also find helpful.

In PHP we can find the absolute value of an integer by using the abs() function. For example if I were trying to work out the difference between two figures I could do this:

$turnover = 10000;
$overheads = 12500;

$difference = abs($turnover-$overheads);

echo "The Difference is ".$difference;

This would produce The Difference is 2500.

answered May 26, 2011 at 7:45

4

I believe this is what you were looking for:

class Expression {
    protected $expression;
    protected $result;

    public function __construct($expression) {
        $this->expression = $expression;
    }

    public function evaluate() {
        $this->result = eval("return ".$this->expression.";");
        return $this;
    }

    public function getResult() {
        return $this->result;
    }
}

class NegativeFinder {
    protected $expressionObj;

    public function __construct(Expression $expressionObj) {
        $this->expressionObj = $expressionObj;
    }

    public function isItNegative() {
        $result = $this->expressionObj->evaluate()->getResult();

        if($this->hasMinusSign($result)) {
            return true;
        } else {
            return false;
        }
    }

    protected function hasMinusSign($value) {
        return (substr(strval($value), 0, 1) == "-");
    }
}

Usage:

$soldPrice = 1;
$boughtPrice = 2;
$negativeFinderObj = new NegativeFinder(new Expression("$soldPrice - $boughtPrice"));

echo ($negativeFinderObj->isItNegative()) ? "It is negative!" : "It is not negative :(";

Do however note that eval is a dangerous function, therefore use it only if you really, really need to find out if a number is negative.

:-)

answered Aug 11, 2012 at 0:59

MahnMahn

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6

if(x < 0)
if(abs(x) != x)
if(substr(strval(x), 0, 1) == "-")

answered May 26, 2011 at 7:52

MartyMarty

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You could check if $profitloss < 0

if ($profitloss < 0):
    echo "Less than 0\n";
endif;

Shakti Singh

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answered May 26, 2011 at 7:46

if ( $profitloss < 0 ) {
   echo "negative";
};

answered May 26, 2011 at 7:46

Tudor ConstantinTudor Constantin

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Don't get me wrong, but you can do this way ;)

function nagitive_check($value){
if (isset($value)){
    if (substr(strval($value), 0, 1) == "-"){
    return 'It is negative
';
} else {
    return 'It is not negative!
';
}
    }
}

Output:

echo nagitive_check(-100);  // It is negative
echo nagitive_check(200);  // It is not negative!
echo nagitive_check(200-300);  // It is negative
echo nagitive_check(200-300+1000);  // It is not negative!

answered Sep 30, 2017 at 23:38

Just multiply the number by -1 and check if the result is positive.

answered Oct 22, 2015 at 11:33

1

You could use a ternary operator like this one, to make it a one liner.

echo ($profitloss < 0) ? 'false' : 'true';

answered Jan 23, 2015 at 10:47

1

Can be easily achieved with a ternary operator.

$is_negative = $profitloss < 0 ? true : false;

answered Nov 13, 2020 at 6:45

Usman AhmedUsman Ahmed

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1

I wrote a Helper function for my Laravel project but can be used anywhere.

function isNegative($value){
    if(isset($value)) {
        if ((int)$value > 0) {
            return false;
        }
        return (int)$value < 0 && substr(strval($value), 0, 1) === "-";
    }
}

answered Jul 2, 2021 at 6:57

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