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What Is an Array? An array is a variable type that can store and index a set of values. An array is useful when the data you want to store has something in common or is logically grouped into a set. Creating and Accessing Arrays Suppose you wanted to store the average temperature for each month of the year. Using single-value variablesalso known as scalar variablesyou would need 12 different variables$temp_jan, $temp_feb, and so onto store the values. By using an array, you can use a single variable name to group the values together and let an index key indicate which month each value refers to.

In general, a script will perform better if you use string functions in place of ereg for simple string comparisons. Testing Sets of Characters As well as checking that a sequence of characters appears in a string, you can test for a set of characters by enclosing them in square brackets. You simply list all the characters you want to test, and the expression matches if any one of them occurs. The following example is actually equivalent to the use of eregi shown earlier in this lesson: if (ereg("[Pp][Hh][Pp]", $phrase)) { echo "The expression matches"; } This expression checks for either an uppercase or lowercase P, followed by an uppercase or lowercase H, followed by an uppercase or lower-case P.

Let's use the email address regular expression as an example. )+([a-z]{2,4})$", $email, $match)) { echo "Mailbox: " . $match[1] . "
"; echo "Domain name: " . $match[2] . "
"; echo "Domain type: " . $match[3] . "
"; } else { echo "Email address is invalid"; } If you run this script in a web browser, you get output similar to the following: Mailbox: chris Domain name: lightwood. Domain type: net Note that the first key of $match refers to the first pattern found. The array keys are numbered from zero, as usual; however, $match[0] contains the entire matched pattern.