PHP - Getting a float variable internal value

Question

I am trying to establish the delta I need when doing float comparison in PHP. I want to take a closer look at my variables to see the difference. I have 2 computed variables, $a, $b. ``` $a = some_function(); $b = some_other_function(); ``` How can I see the exact number which PHP uses? I want to compare them with this formula, where I need to specify the delta: ``` $delta = 0.00001; if (abs($a-$b) < $delta) { echo "identical"; } ``` var_dump($a, $b) returns 1.6215; 1.6215. but I know that they are not exactly equal because ``` var_dump($a === $b); ``` evaluates to false; Why doesn't `var_dump()` print the internal value?

Accepted Answer

In PHP, the printed values of floating point numbers are dependent on PHP configuration "precision".

You can change that with:

```
ini_set('precision', YOUR_DESIRED_PRECISION_AS_INTEGER);
```

For example with with:

```
ini_set('precision', 18);
```

Your numbers may display something like:

float 1.62149999999999994

float 1.6214999999999995

So now the difference between them is clearer.

So your delta may be: $delta = 0.00000000000001; It really depends of the precision you are looking for.

If you need to do exact mathematical calculations, do have a look at the BC Math Functions.

References / Sources

PHP - Floating point numbers

PHP - Floating point numbers - User Contributed Notes - deminy at deminy dot net

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PHP - Getting a float variable internal value

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