1

I have an array that stores numeric values. The issue is when I want to store the value 0:

.... 
$gradePoints = 0;
$students[$var1][$var2] = $gradePoints;
....

To check the value has been stored:

echo $students[$var1][$var2];

returns 0 ... so the value 0 has been successfully stored in the array.

However later when I search the array:

$value= isset($students[$var1][$var2]) ? $students[$var1][$var2] : '';

if ($value <> '')
{
do something;
}

If $value is anything but 0 it is fine but php seems to overlook the value 0. If I change

$gradePoints = 0;

to 

$gradePoints = 0.1;

all is well. Can anyone explain why $value <> '' works for all values other than 0?

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4
  • 'If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically.' nl1.php.net/manual/en/language.operators.comparison.php p.s. so i guess that empty string is converted to 0? Commented Sep 4, 2015 at 21:37
  • Forget about isset. Just try $value = 0; if ($value <> '') { do something } Commented Sep 4, 2015 at 21:38
  • 2
    Don't use a string comparison when testing for numeric values. Set $value to null, or false, and then test for that condition. Commented Sep 4, 2015 at 21:40
  • 2
    And for an explanation of why, see here: stackoverflow.com/questions/28739397/… Commented Sep 4, 2015 at 21:42

2 Answers 2

Reset to default
3

Change:

$value= isset($students[$var1][$var2]) ? $students[$var1][$var2] : '';

if ($value <> '')

To:

$value = isset($students[$var1][$var2]) ? $students[$var1][$var2] : false;

if ($value !== false)

Course there are other ways to do it as well. Bottom line you want to avoid comparing zeros and empty strings, they will get evaluated as the same. Instead use === and !== for a precise comparison.

See here for more details: https://www.php.net/manual/en/language.operators.comparison.php

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6 Comments

Although I have ticked this I am afraid this does not work - if ($value !== '') as Nevermind suggests does though.
If you set the value to false, and then check for !== false, it absolutely works. Show me your code if you are having issues.
The issue it seems with !== false is that it picked up every record ... as it included the '' ones (ie empty as opposed to null)
Then you have an issue somewhere that I can't see. Using concrete null or false is better practice than setting and checking for empty strings. Glad you got it working, but you should revisit how you are solving this.
I agree and thanks for the help. I think it is down to $value= isset($students[$var1][$var2]) ? $students[$var1][$var2] : ''; as this sets the value to be empty if not already set. Perhaps it is better to leave it as null?
|
0

Use this operator (not identical, it will check type of variable, too):

$value=0;



if ($value !== '')
{
//do something
}

You have issues because of type juggling™, as described here: http://php.net/manual/en/language.operators.comparison.php

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1 Comment

LOL mr Down Voter, please provide explanation... If you didn't noticed, i have actually provided an answer in FIRST comment to this post, BEFORE any other answer (mine included)... I think that i explained problem, and did what should be done, in this case... If OP wants to compare value with empty string (for its own reasons), if $value is 0 - this will work. You little egoistic... :)

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