I've found it very helpful to adopt a standard approach to print() and echo() usage.
I almost always use print() in my code. I only use echo() when I'm looking to display bits and pieces which I don't necessarily want to remain in the code when it's finished - eg when I want to display the value of a variable during debugging etc.
Then when I'm wrapping up the code, I can just do a grep for any echos and remove them.