Chapter 3. Arrays, Strings, and Advanced Data Manipulation in PHP

In the previous chapter, we introduced the basics of the PHP language. In this chapter we show you some important techniques you’ll need to manipulate data in PHP. This includes ways of dealing with arrays, strings, dates, and numerical data. The topics in this chapter cover:

  • Arrays and array library functions

  • Strings and string library functions

  • Regular expressions

  • Date and time functions

  • Integer and float functions

We don’t attempt to cover every function and library supported by PHP. However, we provide brief descriptions of them in Appendix E. In later chapters, we discuss selected specialized library functions that support the topics and techniques presented here.


Programmers continually have to deal with collections of data items. For instance, when you query a database for products, you may get a collection with multiple results. In PHP, as with many programming languages, you can handle these results through an array. An array can be considered a name that refers to many related items.

Arrays in PHP are sophisticated and more flexible than in many other high-level languages. A PHP array is an ordered set of variables, in which each variable—called an element— has an associated key . PHP allows elements to be accessed using either string or integer keys—PHP automatically assigns integer key values if keys are not specified when arrays are constructed.

Arrays can hold scalar values (integers, Booleans, strings, ...

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