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The PHP Math is_nan() function is used to check if the argument is "not a number" or not. It returns true (1) if the argument is "not a number", else returns false/nothing.

Syntax

is_nan(x)   

Parameters

x Required. Specify the value.

Return Value

Returns true (1) if the argument is "not a number", else returns false/nothing.

Example:

In the below example, is_nan() function is used to check if the argument is "not a number" or not.

<?php
echo var_dump(is_nan(2));
echo var_dump(is_nan(log(-1)));
echo var_dump(is_nan(acos(5)));    
?>

The output of the above code will be:

bool(false)
bool(true)
bool(true)

❮ PHP Math Functions