A regular expression assistant
Although there's no doubt that regular expressions are incredibly useful, they also easily get out of hand when trying to match complex strings. Furthermore, anything past twelve or so characters gets hard to read and understand, which is a common source of bugs.
To work around this problem, I suggest you use an online site such as
Regex101.com, which helps you check your regular expressions are correct by visually highlighting strings that match. It's fully compatible with all the options shown here, including string replacement, and can even break down a regex and describe it in plain English.
Next chapter: Checking whether a function is available >>
Regular expression syntax examples
Functions Functions overview How to read function prototypes Working with variables Controlling script execution Working with Date and Time Reading the current time Converting from a string Converting to a string Converting from components Mathematics Rounding Randomisation Trigonometrical conversion Other mathematical conversion functions Base conversion Mathematical constants Playing with strings Reading from part of a string Replacing parts of a string Converting to and from ASCII Measuring strings Finding a string within a string Returning the first occurrence of a string Trimming whitespace Wrapping your lines Changing string case Making a secure data hash Alternative data hashing Automatically escaping strings Pretty-printing numbers Removing HTML from a string Comparing strings Padding out a string Complex string printing Parsing a string into variables Regular expressions Basic regexes with preg_match() and preg_match_all() Novice regexes Advanced regexes Guru regexes Regular expression replacements Regular expression syntax examples A regular expression assistant Checking whether a function is available Extension functions Pausing script execution Executing external programs Connection-related functions Altering the execution environment User functions Return values Parameters Passing by reference Returning by reference Default parameters Variable parameter counts Variable scope in functions Overriding scope with the GLOBALS array Recursive functions Variable functions Callback functions The declare() function and ticks Handling non-English characters Undocumented functions Summary Exercises Further reading Next chapter
Table of Contents
Copyright ©2015 Paul Hudson.
Follow me: @twostraws.