PHP 5/MySQL Programming- P37 pps

Finding a Substring with substr() The algorithm’s behavior depends on the first character of each word. I need to know all the rest of the word without the first character. 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. It’s not much more complicated to get the rest of the word: $restOfWord = substr($theWord, 1, strlen($theWord) -1); Once again, I need to extract values from $theWord. This time I begin at character 1 (which humans would refer to as the second character ). I don’t know directly how many characters to get, but I can calculate it. I should grab one less charac- ter than the total number of characters in the word. The strlen() function is per- fect for this operation, because it returns the number of characters in any string. I can calculate the number of letters I need with strlen($theWord) – 1. This new decapitated word is stored in the $restOfWord variable. Using strstr() to Search for One String Inside Another The next task is to determine if the first character of the word is a vowel. You can take a number of approaches to this problem, but perhaps the easiest is a search- ing function. I created a string with all the vowels ( “aeiouAEIOU”) and then I searched for the existence of the $firstLetter variable in the vowel string. The strstr() function is perfect for this task. It takes two parameters: the string you are looking for (given the adorable name haystack in the online documenta- tion) and the string you are searching in (the needle ). To search for the value of the $firstLetter variable in the string constant “aeiouAEIOU”, I used the following line: if (strstr(“aeiouAEIOU”, $firstLetter)){ 158 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r The strstr() function returns the value FALSE if the needle was not found in the haystack. If the needle was found, it returns the position of the needle in the haystack parameter. In this case, I’m really concerned only whether $firstLetter is found in the list of variables. If so, it’s a vowel, which changes the way I modify the word. Using the Concatenation Operator Most of the time in PHP you can use string interpolation to combine string val- ues. However, sometimes you need a formal operation to combine strings. The process of combining two strings is called concatenation. (I love it when simple ideas have complicated names.) The period ( .) is PHP’s concatenation operator. If a word in pig Latin begins with a vowel, it should end with the string “way”. I used string concatenation to make this work: $newWord = $theWord . “way”; When the word begins with a consonant, the formula for creating the new word is slightly more complicated, but is still performed with string concatenation: $newWord = $restOfWord . $firstLetter . “ay”; Recent testing has shown that the concatenation method of building strings is dramatically faster than interpolation. If speed is an issue, you might want to use string concatenation rather than string interpolation. Finishing the Pig Latin Program Once I created the new word, I added it and a trailing space to the $newPhrase variable. When the foreach loop has finished executing, $newPhrase contains the pig Latin translation of the original phrase. Translating Between Characters and ASCII Values Although it isn’t necessary in the pig Latin program, the Word Search program requires the ability to randomly generate a character. I do this by randomly gen- erating an ASCII value and translating that number to the appropriate character. (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. TRICK 159 C h a p t e r 5 B e t t e r A r r a y s a n d S t r i n g H a n d l i n g To get a random uppercase letter, I can use the following code: $theNumber = random(65, 90); $theLetter = ord($theNumber); Returning to the Word Search Creator The Word Search program is stored in three files. First, the user enters a word list and puzzle information into an HTML page. This page calls the main wordFind.php program, which analyzes the word list, creates the puzzle, and prints it out. Finally, the user has the opportunity to print an answer key, which is created by a simple PHP program. Getting the Puzzle Data from the User The wordFind.html page is the user’s entry point into the word find system. This page is a standard HTML form with a number of basic elements: <html> <head> <title>Word Puzzle Maker</title> </head> <body> <center> <h1>Word Puzzle Maker</h1> <form action = “wordFind.php” method = “post”> <h3>Puzzle Name</h3> <input type = “text” name = “name” value = “My Word Find”> height: <input type = “text” name = “height” value = “10” size = “5”> width: <input type = “text” name = “width” value = “10” size = “5”> <br><br> 160 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r <h3>Word List</h3> <textarea rows=10 cols=60 name = “wordList”></textarea> <br><br> Please enter one word per row, no spaces <br> <input type=”submit” value=”make puzzle”> </form> </center> </body> </html> The form’s action property points to the wordFind.php program, which is the pri- mary program in the system. I used the post method to send data to the program because I expect to send large strings to the program. The get method allows only small amounts of data to be sent to the server. The form features basic text boxes for the puzzle name, height, and width. This data determines how the puzzle is built. The wordList text area is expected to house a list of words, which create the puzzle. Setting Up the Response Page The bulk of the work in the wordFind system happens in the wordFind.php page. This program has a small amount of HTML to set the stage, but the vast bulk of this file is made up of PHP code. <html> <head> <title> Word Find </title> </head> <body> <? // word Find // by Andy Harris, 2003 // for PHP/MySQL programming for the Absolute Beginner // Generates a word search puzzle based on a word list // entered by user. User can also specify the size of // the puzzle and print out an answer key if desired 161 C h a p t e r 5 B e t t e r A r r a y s a n d S t r i n g H a n d l i n g Notice the comments at the beginning of the code. Since this program’s code is a little more involved than most of the programs you have seen in this book, I decided to comment it more carefully. My comments here basically lay out the plan for this program. It’s a really good idea to add comments to your programs so you can more easily determine what they do. You’ll be amazed how little you understand your own code after you’ve been away from it for a couple of days. Good comments can make it much easier to maintain your code, and make it easier for others to fix and improve your programs later. Working with the Empty Data Set For testing purposes, I wrote the Word Search PHP page before I worried about the HTML. For that reason, I simply added default values for a word list and for the other main variables that determine the board’s layout (height, width, and name). In a production version of the program, I don’t expect the PHP code to ever be called without an HTML page, but I left the default values in place so you could see how they work. if ($wordList = = NULL){ //make default puzzle $word = array( “ANDY”, “HEATHER”, “LIZ”, “MATT”, “JACOB” ); $boardData = array( width => 10, height => 10, name => “Generic Puzzle” ); This code builds two arrays, which define the entire program. The $word array holds the list of words to hide in the puzzle, and $boardData is an associative array holding critical information about how the board is to be created. Of course, I don’t expect to use these values, because this program usually is called from an HTML form, which generates the values. The next section of code fills up these variables if the program is called from the appropriate form. 162 P H P 5 /M y S Q L P r o g r a m m i n g f o r t h e A b s o l u t e B e g i n n e r . main wordFind .php program, which analyzes the word list, creates the puzzle, and prints it out. Finally, the user has the opportunity to print an answer key, which is created by a simple PHP program. Getting. wordFind system happens in the wordFind .php page. This program has a small amount of HTML to set the stage, but the vast bulk of this file is made up of PHP code. <html> <head> <title> Word. vowel, which changes the way I modify the word. Using the Concatenation Operator Most of the time in PHP you can use string interpolation to combine string val- ues. However, sometimes you need a formal