Why is this expression automatically rounding on me?

[wbednarz]

I am very new to PHP and programming in general. About 3 weeks into this.

I have this simple expression and some echo in my code.

 

    $x1 = $lat_b + $lat_a1;

    echo "<br>lat b: ".$lat_b;

    echo "<br>lat a1: ".$lat_a1;   

    echo "<br>x1: ".$x1;

 

$lat_b and $lat_a1 are derived from some xml extractions from a yahoo geocode api (that part works fine).

 

The results of the expression and echos above are as follows:

 

    lat b: 40.402866

    lat a1: 40.252590

    x1: 80

 

Why is $x1 rounding automatically on me?

 

Later, I substituted the expression above with  $x1 = 40.402866 + 40.252590 ; The new result (shown below) makes sense to me.

 

  lat b: 40.402866

  lat a1: 40.252590

  x1: 80.655456

 

[Pikachu2000]

Hard to say what's happening there. When I paste your original code block in and run it locally, it produces the correct result. Did you check the html source to make sure something isn't getting mangled somehow?

 

lat b: 40.402866
lat a1: 40.25259
x1: 80.655456

[mentalist]

It works fine for me... But I do remember having this problem years ago!

One, try using sprintf to format the output (http://uk3.php.net/manual/en/function.sprintf.php)

 

Otherwise try initialising $c to a float.

$c=0.0;

[wbednarz]

The datatypes of $lat_b and $lat_a1 were set to object. This was from the xml extraction (see example below). I added the (float) type casting attribute to the expression to fix the problem. Thanks for the help.

 

$xml_a1=simplexml_load_file("http://where.yahooapis.com/geocode?location={$score_capabilities_z1['si_cmp_zip']}=myapiid");   

$lat_a1= (float) $xml_a1->Result->latitude;

[mentalist]

Well done, so this is solved then!

[wbednarz]

The next expression, which is more complicated, has a similar issue. The (float) attribute in the expression does not seem to solve the problem this time. It looks like rounding is occurning within the expression.

 

    $score_capabilities_d1= (float) ((69.1*($lat_b-$lat_a1))^2+(53*($lon_b-$lon_a1)*cos($lat_a1/57.3))^2)^0.5;

 

The result of this variable should be 10.4238... Instead, I just get 10.

 

I am taking geocode data (latitude and longitudes from a zip code) of two locations and trying to get the distance between them.

 

Well done, so this is solved then!

[mentalist]

you'll need to add 'float' in a few more places then...

[wbednarz]

I figured I should post the solution to this problem. When I used a carat to square (and square root) a portion of the expression, the data type would change to integer. Not sure why this is the case. I used the pow(x,y) and sqrt()  functions to fix this.

 

    $score_capabilities_d1=round(sqrt(pow(69.1*($lat_b-$lat_a1),2)+pow(53*($lon_b-$lon_a1)*cos($lat_a1/57.3),2)),1);

 

The next expression, which is more complicated, has a similar issue. The (float) attribute in the expression does not seem to solve the problem this time. It looks like rounding is occurning within the expression.

 

    $score_capabilities_d1= (float) ((69.1*($lat_b-$lat_a1))^2+(53*($lon_b-$lon_a1)*cos($lat_a1/57.3))^2)^0.5;

 

The result of this variable should be 10.4238... Instead, I just get 10.

 

I am taking geocode data (latitude and longitudes from a zip code) of two locations and trying to get the distance between them.

 

Well done, so this is solved then!

[PFMaBiSmAd]

^ is an exclusive or bitwise operator, not a mathematical operator.