PHP is_nan() Function

The is_nan() function in PHP checks whether a given value is NaN (Not a Number). This is particularly useful when working with mathematical operations that might produce invalid results.

Syntax

is_nan ( float $val ) : bool

Parameters

Return Value

Returns true if the value is NaN, false otherwise.

Example

The following example demonstrates how is_nan() works with various mathematical operations that produce NaN ?

<?php
// Operations that produce NaN
$val1 = sqrt(-1);      // Square root of negative number
$val2 = acos(2);       // Arc cosine of value > 1
$val3 = log(-5);       // Logarithm of negative number

// Test each value
echo "sqrt(-1): ";
var_dump($val1);
echo "is_nan result: " . (is_nan($val1) ? 'true' : 'false') . "<br><br>";

echo "acos(2): ";
var_dump($val2);
echo "is_nan result: " . (is_nan($val2) ? 'true' : 'false') . "<br><br>";

echo "log(-5): ";
var_dump($val3);
echo "is_nan result: " . (is_nan($val3) ? 'true' : 'false') . "<br><br>";

// Valid number
$val4 = sqrt(25);
echo "sqrt(25): ";
var_dump($val4);
echo "is_nan result: " . (is_nan($val4) ? 'true' : 'false');
?>

The output of the above code is ?

sqrt(-1): float(NAN)
is_nan result: true

acos(2): float(NAN)
is_nan result: true

log(-5): float(NAN)
is_nan result: true

sqrt(25): float(5)
is_nan result: false

Key Points

Important considerations when using is_nan():

• NaN values are created by invalid mathematical operations
• NaN is not equal to any value, including itself
• Available in PHP 4.x, 5.x, 7.x, and 8.x
• Accepts only float values as parameter

Conclusion

The is_nan() function is essential for validating mathematical calculations in PHP. Use it to detect invalid results from operations like square roots of negative numbers or logarithms of non-positive values.