PHP Java Properties

Java typically stores its configuration in files that end with a .properties extension. These files are essentially key-value pairs of data. Java SE has a built-in class, java.util.Properties, for reading and writing these files.

Sometimes, though, you may want to read these files from other languages. For example, database information is often stored in a .properties file. If another application wishes to connect to the same database, it is better to read that file rather than create a copy. That way, if the password changes (for example), you only have one place to update.

The basic syntax of the file is easy to understand. It is line-based. Each line is either a blank line, a comment line, or a key-value pair. Keys are separated from values by an =, :, or space. Easy, right?

Well, there are a few complications. You can read the full spec here, but this is a brief summary of some of the issues with creating a fully-compliant reader/writer:

• An odd number of backslashes indicates that the next line is a continuation of the previous line, unless the line is a comment line, which can't be continued
• Comments are started with # or !, and extend to the end of the line; however, if a # or ! appears after the first non-whitespace character, they are not considered to be comments. When writing, though, these values are still escaped using a backslash.
• =, :, or space separate a key from a value.  However, these values can be escaped so that they can be used as part of a key or value string.

So here is a working PHP port of the java.util.Properties class. Most of the common methods are implemented with the same name as their Java counterpart.  The header documentation of the class goes into more details on what is and is not implemented, and where to find the corresponding functionality.

Download here