The is_nan function is a very practical tool to check if a value is "non-number" (NaN). It returns a Boolean value, which returns true if the value passed in is NaN (i.e. not a valid number), otherwise returns false.

We can use the sprintf() function to format the string. And array_map() is a very useful function that applies a callback function to every element in an array. If we want to format each element in the array quickly, we can use these two functions to achieve this. This article will explain how to use sprintf() and array_map() to quickly format each element in an array.