Chapter 5 BET TER ARRAYS AND STRINGS HANDLING

Transcription

1 Chapter 5 BET TER ARRAYS AND STRINGS HANDLING

2 Chapter Objective Manage arrays with the foreach loop Create and use associative arrays Extract useful information from some of PHP s built-in arrays Build basic two-dimensional arrays Build two-dimensional associative arrays Break a string into smaller segments Search for one string inside another

3 foreach loop The foreach loop works a lot like a for loop. The first parameter of the foreach construct is an array in this case, $list. The keyword as indicates the name of a variable that holds each value in turn. In this case, the foreach loop steps through the $list array as many times as necessary. Each time through the loop, the function populates the $value variable with the current member of the $list array

4 foreach The foreach loop can be an extremely handy shortcut for stepping through each value of an array. Since this is a common task, knowing how to use the foreach loop is an important skill.

5 Associative Array The associative array is just like a normal array, except the index values are strings. Note that the indices must be inside quotation marks. Once you have created an associative array, it is used much like a normal array.

6 Building an Associative Array with the array() Function If you know the values you want in your array, you can use the array() function to build an associative array. The array() function requires the data when you are building an ordinary array, but doesn t require specified indices. The for normal arrays the function automatically generates each element s index by grabbing the next available integer. In an associative array, you are responsible for providing both the data and the index.

7 foreach loop associative array A foreach loop for a regular array uses only one variable because the index can be easily calculated. In an associative array, each element in the array has a unique index and value. The associative form of the foreach loop takes this into account by indicating two variables. The first variable holds the index. The second variable refers to the value associated with that index.

8 Reading the $_REQUEST Array All forms store data in a few associative arrays, one of which is called $_REQUEST which store all the name and values of a submitted form. If you have a form with a field called username, you can get the value of the field by calling $_REQUEST[ username ]. To print all names and values on any form:

9 Multidimensional Array A multidimensional array, acts much like table data like the one below. Imagine you were trying to write a program to help users determine the distance between major cities.

10 basicmultiarray program Note each option value. This will be used later. Lets build the form to call up the data from a Multidimensional Array. When the user submits this form, it sends two variables. The citya variable contains the value property associated with whatever city the user selected; cityb likewise contains the value of the currently selected destination city. Page 166

11 Create Multidimensional Array Array of Arrays Note the order of the cities. The same order was used when creating the form and the same order was used to create the multidimensional array. The value of citya and cityb the user select in the form. The city name that corresponded to the value. Since we know the order the cities were listed it easy to pull up. CityA and CityB are the index values for the multidimensional array.

12 Create Multidimensional Array Distance from New York to London CityA=New York Value: 1 CityB=London Value: 3 Reminder we start at 0

13 Associative Multidimensional Array Notice the values are now strings and not number as in the previous example.

14 Building a Associative Multidimensional Array Each entry in the array uses a city name as the index (indy, ny, tokyo, london). The index points to an array with the distance relative from itself. Inside the array, the city names as indices. The value for each index refers to the distance from the current city (Indianapolis) to the particular destination. The distance from Indianapolis to Indianapolis is 0, and the distance from Indy to New York is 648, and so on.

15 Getting Data from a Two-Dimensional Associative Array The city names themselves are used as indices, so there s no need for a separate array to hold city names. Once the city names are extracted from the form, the data can be output in two lines of code:

16 Break a String into an Array The split() function takes a string and breaks it into an array based on some sort of delimiter, or separator character. The split() function takes two arguments. The first argument is a delimiter and the second is a string to break up. Example: Delimiter a blank space $inputstring = My Long String ; $words = split(" ", $inputstring); Array=(M, y, L, o, n, g, S, t, r, i, n, g)

17 Trimming a String with rtrim() PHP provides a function called rtrim() which automatically removes spaces, tabs, newlines, and other whitespace from the end of a string. You can used the rtrim() function to clean off any trailing spaces from the split() operation and returned the results to a variable.

18 Finding a Substring with substr() The substr() function is useful for getting part of a string. It requires three parameters: The string you want to get a piece from Which character you want to begin with (starting with 0 as usual) How many characters you want to extract I got the first letter of the word with this line: $firstletter = substr($theword, 0, 1); It gets one letter from $theword starting at the beginning of the word (position 0). I stored that value in the $firstletter variable.

19 strstr() to Search for One String Inside Another The strstr() function takes two parameters: The string you are looking for (given the adorable name haystack in the online documentation) The string you are searching in (the needle). To search for the value of the $firstletter variable in the string constant aeiouaeiou, use the following line: if (strstr("aeiouaeiou", $firstletter)){ }

20 Concatenation Operator The process of combining two strings is called concatenation. The period (.) is PHP s concatenation operator.

21 Translating Between Characters and ASCII Values ASCII is the code used to store characters as binary numbers In the computer s memory. The ord() function is useful in this situation. The uppercase letters are represented in ASCII by numbers between 65 and 90.

22 Word Search Creator Page 179 : Sample code that uses all the above topics to generate a Work Search Game.

23 Comparing Strings Exact Comparisons == casts non-string operands to strings === no castings; returns false if types differ <, <=, >, >= OK with strings if one operand is a number, other operand is cast to a number strcmp(string_1, string_2 [, len]) for string comparison; casts numbers to strings returns negative number, 0, or positive number strcasecmp(string_1, string_2 [, len]) converts strings to lowercase before comparing natural-order comparison strnatcmp(string_1, string_2 [, len]) strnatcasecmp(string_1, string_2 [, len]) handles numeric portions of strings the natural way