This chapter introduces many of the PHP functions that you??™ll undoubtedly use
on a regular basis when performing such tasks.
This chapter covers the following topics:
??? Regular expressions: A brief introduction to regular expressions touches upon
the features and syntax of PHP??™s two supported regular expression implementations:
POSIX and Perl. Following that is a complete introduction to PHP??™s
respective function libraries.
??? String manipulation: It??™s conceivable that throughout your programming
career, you??™ll somehow be required to modify every possible aspect of a string.
Many of the powerful PHP functions that can help you to do so are introduced
in this chapter.
??? The PEAR Validate_US package: In this and subsequent chapters, various PEAR
packages are introduced that are relevant to the respective chapter??™s subject
matter. This chapter introduces Validate_US, a PEAR package that is useful for
validating the syntax for items commonly used in applications of all types,
including phone numbers, Social Security numbers (SSNs), ZIP codes, and state
abbreviations. (If you??™re not familiar with PEAR, it??™s introduced in Chapter 11.)
232 CHAPTER 9 ?– STRINGS AND REGULAR EXPRESSIONS
Regular Expressions
Regular expressions provide the foundation for describing or matching data according
to defined syntax rules. A regular expression is nothing more than a pattern of characters
itself, matched against a certain parcel of text.
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