Writing PHP code in your regular word-processing editor like Microsoft Word is not an option. It’ll add all sorts of junk (e.g. style definitions, proprietary characters, etc.) to your document — and PHP isn’t able to process that junk. You’ll need a text editor to writing, editing and debugging PHP such as:

• Notepad++ (free)
• Phpdesigner
• Adobe Dreamweaver
• Zend Studio 8.1

or see This full list

Syntax Highlighting is Important

So you open Notepad and you’re ready to start writing a few lines of code. It’s time to test what you’ve written and PHP tells you that you forgot a single quote on line X, and it is therefore unable to run your script. If you are working with "a few lines of code," it won’t be hard to determine where you forgot the single quote. But what if there are a "few thousand lines of code"? Meet syntax highlighting. When enabled, instructions, declarations and so forth will have their own color (it’s not added to the document, so no junk!). Even without knowing what the following piece of code does, it will only take a second to find the missing single quote. Finding the missing single quote is a piece of cake with syntax highlighting enabled.