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Using Variables for More-Complex Pages While the Hello Jacob program was interesting, there is no real advantage to using a variable. Check out another use for variables. Building the Row Your Boat Page Figure 2.5 shows the Row Your Boat page. I chose this song in particular because it repeats the same verse three times. If you look at the original code for the rowBoat.php program, you see I used a trick to save some typing: <html> <head> <title>Row Your Boat</title> </head> <body> <h1>Row Your Boat</h1> <h3>Demonstrates use of long variables</h3> <? $verse = <<<HERE 28 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 FIGURE 2.5 This program shows the words to a popular song. They sure repeat a lot. Row, Row, Row, your boat<br> Gently Down the stream<br> Merrily, Merrily, Merrily, Merrily<br> Life is but a dream!<br> <br><br> HERE; print “<h3>Verse 1:</h3>”; print $verse; print “<h3>Verse 2:</h3>”; print $verse; print “<h3>Verse 3:</h3>”; print $verse; ?> </body> </html> Creating Multi-Line Strings You find yourself wanting to print several lines of HTML code at once. It can be very tedious to use quotation marks to indicate such strings (especially because HTML also often uses the quotation mark symbol). PHP provides a special quoting mechanism, which is perfect for this type of situation. The following line begins assigning a value to the $verse variable: $verse = <<<HERE The <<<HERE segment indicates this is a special multi-line string that ends with the symbol HERE. You can use any phrase you wish, but I generally use the word HERE because I think of the three less-than symbols as up to. In other words, you can think of the following as meaning verse gets everything up to HERE. $verse = <<<HERE You can also think of <<<HERE as a special quote sign, which is ended with the value HERE. You can write any amount of text between <<<HERE and HERE. You can put vari- ables inside the special text and PHP replaces the variable with its value, just like in ordinary (quoted) strings. The ending phrase ( HERE) must be on a line by itself, and there must be no leading spaces in front of it. 29 C h a p t e r 2 U s i n g V a r i a b l e s a n d I n p u t You might wonder why the $verse = <<<HERE line doesn’t have a semicolon after it. Although this is one line in the editor, it begins a multi-line structure. Technically, everything from that line to the end of the HERE; line is part of the same logical line, even though the code takes up several lines in the editor. Everything between <<<HERE and HERE is a string value. The semicolon doesn’t have any special meaning inside a string. At a minimum, you should know that a line beginning a multi-line quote doesn’t need a semi- colon, but the line at the end of the quote does. Once the multi-line string is built, it is very easy to use. It’s actually harder to write the captions for the three verses than the verses themselves. The print statement simply places the value of the $verse variable in the appropriate spots of the output HTML. Working with Numeric Variables Computers ultimately store information in on/off impulses. You can convert these very simple data values into a number of more convenient kinds of infor- mation. The PHP language makes most of this invisible to you, but it’s important to know that memory handles string ( text ) differently than it does numeric values, and that there are two main types of numeric values, integers, and floating- point real numbers. Making the ThreePlusFive Program As an example of how PHP works with numbers, consider the ThreePlusFive.php program illustrated in Figure 2.6. All the work in the ThreePlusFive program is done with two variables called $x and $y. (I know, I recommended that you assign variables longer, descriptive names, but these variables are commonly used in arithmetic problems, so these very short variable names are okay in this instance.) The code for the program looks like this: <html> <head> <title>Three Plus Five</title> </head> <body> <h1>Three Plus Five</h1> <h3>Demonstrates use of numeric variables</h3> TRAP 30 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 <? $x = 3; $y = 5; print “$x + $y = “; print $x + $y; print “<br><br>”; print “$x - $y = “; print $x - $y; print “<br><br>”; print “$x * $y = “; print $x * $y; print “<br><br>”; print “$x / $y = “; print $x / $y; print “<br><br>”; ?> </body> </html> 31 C h a p t e r 2 U s i n g V a r i a b l e s a n d I n p u t FIGURE 2.6 This program does basic math on variables containing the values 3 and 5. 32 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 Assigning Numeric Values You create a numeric variable like any other variable in PHP: Simply assign a value to a variable. Notice that numeric values do not require quotation marks. I created variables called $x and $y and assigned appropriate values to these variables. Using Mathematical Operators For each calculation, I want to print the problem as well as its solution. This line prints out the values of the $x and $y variables with the plus sign between them: print “$x + $y = “; In this particular case (since $x is 3 and $y is 5), it prints out this literal value: 3 + 5 = Because the plus and the equals signs are inside quotation marks, they are treated as ordinary text elements. PHP doesn’t do any calculation (such as addi- tion or assignment) with them. The next line does not contain any quotation marks: print $x + $y; It calculates the value of $x + $y and prints the result (8) to the Web page. IN THE REAL WORLD Numbers without any decimal point are called integers and numbers with dec- imal values are called real numbers. Computers store these two types differ- ently, and this distinction sometimes leads to problems. PHP does its best to shield you from this type of issue. For example, since the values 3 and 5 are both integers, the results of the addi- tion, subtraction, and multiplication problems are also guaranteed to be inte- gers. However, the quotient of two integers is often a real number. Many languages would either refuse to solve this problem or give an incomplete result. They might say that 3 / 5 = 0 rather than 0.6. PHP tries to convert things to the appropriate type whenever possible, and it usually does a pretty good job. You sometimes need to control this behavior, however. The setType() function lets you force a particular variable into a particular type. You can look up the details in the online Help for PHP (included in the CD that accompanies this book). . floating- point real numbers. Making the ThreePlusFive Program As an example of how PHP works with numbers, consider the ThreePlusFive .php program illustrated in Figure 2.6. All the work in the ThreePlusFive. marks to indicate such strings (especially because HTML also often uses the quotation mark symbol). PHP provides a special quoting mechanism, which is perfect for this type of situation. The following. of text between <<<HERE and HERE. You can put vari- ables inside the special text and PHP replaces the variable with its value, just like in ordinary (quoted) strings. The ending phrase
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