PHP Math functions is_nan
We can check a input or variable is a number or not by using is_nan function. Note that we can't check a string with this function.
We can check square root of a negative number with is_nan function. Here is a sample code to check.
$v = acos(1.1);
Out put is
echo "this is not a number";
echo "this is a number";
this is not a number
You can change the line $v=acos(1.1) with different values of variable $v and see the result.
$v=5.23; // this is a number
$v=4; // this is a number
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