Strings Treatment in QCubed

This direcotry contains documents describing methods used for working with string in QCubed.

## QString Class

QCubed is an object-oriented framework. QString class contains methods designed for working with string. These methods are public static and the class itself is an abstract class and thus cannot be instantiated. The methods in this class are described below.

NOTE: Remember to check the class out and read the comments to gain more understanding about what we do.

Methods in QString

• FirstCharacter: Gets first character of a supplied string. This method can operate on multi-byte encodings, of which it considers UTF-8 as default (default encoding is set in the configuration file using __QAPPLICATION_ENCODING_TYPE__ named constant).
• LastCharacter: Gets the last character of a supplied string. Multi-byte encoding is similar to that of FirstCharacter method.
• StartsWith: Checks if a string starts with another sub-string.
• EndsWith: Checks if a string ends with another sub-string.
• Truncate: Truncates the string to a given length, adding elipses (if needed).
• LongestCommonSubsequence: Finds longest substring which is common among two strings. Can be used for analysing differences between two strings.
• Base64UrlSafeEncode: Returns Base64 encoded string for a given data which can be used safely as part of URLs and HTML forms. More about this function has been described below.
• Base64UrlSafeDecode: Decodes string encoded by Base64UrlSafeEncode.

Why Base64UrlSafeEncode

If you do not know about base64, read a primer on Wikipedia: https://en.wikipedia.org/wiki/Base64

You might wonder why QCubed contains a method for base64 encoding (and one for decoding) when PHP already provides one?

Let us look at Base64 character set. Base64 encoded string may contain

• A-Z (capital A to capital Z)
• a-z (small A to small Z)
• 0-9 (digits)
• Characters +, / and = (+ and / form part of encoded data while = can act as padding at the end)

The special characters +, / and = have special values in URLs and HTML form submissions:

• + converts into a single blank space
• / is directory separator in URLs
• = is a key-value separator/delimiter in URL encoded data (in both GET and POST requests)

Hence a raw base64 encoded string may not be safe for all kinds of uses. Base64UrlSafeEncode replaces

• + with -
• / with '_'
• = with blank string (since = is for padding anyways)

This replacement makes the resulting string safe for use in URLs and HTML form submissions, which is the aim of Base64UrlSafeEncode method.