From the blog:
Human readable file sizes
size_readable()
converts a number of bytes into human readable form.
Highlighting a search string in HTML text
str_highlight()
provides a variety of text highlighting options for plaintext or HTML strings.
Handling tab to space conversions
tab2space()
converts tabs to the appropriate amount of spaces to preserving formatting.
Cycling between strings, a novel implementation
Cycle
provides a novel way to iterate through an array. This is commonly used for zebra-striping tables.
Creating a string exerpt elegantly
str_chop()
provides a number of options for trimming long text into something suitable for display.
Converting HTML colours from HEX to RGB
hex2rgb()
converts HTML hexadecimal colour codes into their RGB equivalent
Converting arrays to human readable tables
array2table()
allows you to quickly display the contents of an array as a HTML table. It can also recursively display data for nested arrays.
Calculating a directories size in PHP
dirsize
provides a heavily optimised method for calculating the size of large directories.