Is it possible in PHP to prevent "Fatal error: Call to undefined function"?

In PHP, is there any way that I can ignore functions that are undefined instead of throwing a fatal error that is visible in the browser?—i.e., Fatal error: Call to undefined function

I know that there is the practice of wrapping all custom functions in a conditional as below, but is there a programmatic way to get this effect?

if (function_exists('my_function')) { 

   // use my_function() here;

}