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phpis-empty

PHP: check if empty line ("\n")

I'm using an API in order to retrieve some temperature and location values in JSON format. I'm writing the output in a plain text cachefile.

However a temperature station may fail reporting the temperature value, and in that case my output will be an empty line (\n). I want to handle such case by displaying "N/A" for a non-reporting station.

Here's a typical cachefile with the first station reporting temperature and location, and the second station shut down (reporting two empty lines):

27.6
Napoli-Posillipo
(an empty line)
(an empty line)

I tried with:

$display = file($cachename);
$temperature[0] = $display[0];
$location[0] = $display[1];
$temperature[1] = $display[2];
$location[1] = $display[3];

$temp_avg = (($temperature[0]+$temperature[1])/2); //average temperature

if($temperature[0] = "\n"){ //if weather station is not reporting data
   $temperature[0] = "N/A";
   $temp_avg = "N/A";
}

if($temperature[1] = "\n"){
   $temperature[1] = "N/A";
   $temp_avg = "N/A";
}


echo "<div id='temperature'><b>".$temperature[0]."</b>°C (".$location[0].") | ";
echo "<b>".$temperature[1]."</b>°C (".$location[1].") | ";
echo "<b>".$temp_avg."</b>°C (avg) | ".$minutes."m".$secondsleft."s ago</div>";

However I keep getting "N/A" for both stations, even if the first station correctly reports its temperature value.

N/A°C (Napoli-Posillipo ) | N/A°C () | N/A°C (avg) | 12m21s ago

I tried with fgets() instead of file(), but I got an error:

fgets() expects parameter 1 to be resource, string given in [...] on line 54

I also tried using if(empty($temperature[foo])) but it didn't work, because of course \n != empty.

Any hints? Thanks in advance

Solution

  • Your comparisons should look like this (note the use of two equal signs):

    if($temperature[0] == "\n"){

    Your current code is assigning "\n" to $temperature[1], which evaluates true, which is why the if condition is executing.

    If you would like to use empty(), which I suggest you do, change your call to file() to:

    $display = file($cachename, FILE_IGNORE_NEW_LINES);

    Adding the FILE_IGNORE_NEW_LINES flag will tell the function not to add newlines ("\n") to the end of the array elements.