tailieunhanh - PHP and MySQL Web Development - P22

PHP and MySQL Web Development - P22: PHP and MySQL Web Development teaches the reader to develop dynamic, secure, commercial Web sites. Using the same accessible, popular teaching style of the first edition, this best-selling book has been updated to reflect the rapidly changing landscape of MySQL and PHP. | 72 Chapter 3 Using Arrays Tires Oil Spark Plugs ----------------------------- product Figure Bob s products can be stored in an array. After we have the information as an array we can do a number of useful things with it. Using the looping constructs from Chapter 1 we can save work by performing the same actions on each value in the array. The whole set of information can be moved around as a single unit. This way with a single line of code all the values can be passed to a function. For example we might want to sort the products alphabetically. To achieve this we could pass the entire array to PHP s sort function. The values stored in an array are called the array elements. Each array element has an associated index also called a key that is used to access the element. Arrays in most programming languages have numerical indexes that typically start from zero or one. PHP supports this type of array. PHP also supports associative arrays which will be familiar to Perl programmers. Associative arrays can have almost anything as the array indices but typically use strings. We will begin by looking at numerically indexed arrays. Numerically Indexed Arrays These arrays are supported in most programming languages. In PHP the indices start at zero by default although you can alter this. Initializing Numerically Indexed Arrays To create the array shown in Figure use the following line of PHP code products array Tires Oil Spark Plugs This will create an array called products containing the three values given Tires Oil and Spark Plugs . Note that like echo array is actually a language construct rather than a function. Depending on the contents you need in your array you might not need to manually initialize them as in the preceding example. If you have the data you need in another array you can simply copy one array to another using the operator. If you want an ascending sequence of numbers stored in an array you can use the range function to automatically create the