Xhtml source code gen-
erated by the PHP script.
Although this normally
has no effect on the Web
browser display, it makes
the XHTML source code
easier to read and debug.
The print statement
automatically appends a
“new line” character to
the string it returns.
The following code shows another example of an escape character,
this time with the double quotation escape sequence (\"). Figure 3-4
shows the output.
$Speaker = "Julius Caesar";
echo "<p>\"Et tu, Brute!\" exclaimed $Speaker.</p>";
Figure 3-4
Using escape sequences for double quotes
CHAPTER
3
Manipulating
Strings
130
Because
the string in the previous example contained a variable, the
string
would not display as intended if you used single quotes around
it,
as discussed previously. Remember from Chapter 1 that vari-
ables
are not expanded when the string is enclosed in single quotes.
Similarly,
the escape sequences listed in Table 3-1 will be treated as
literal
text if the string is enclosed in single quotes.
An
alternative to using the double quotation mark escape sequence
is
to use single quotation marks for the starting text portion of the
literal
string and then combine the $Speaker
variable
with the con-
catenation
operator, as follows:
$Speaker
= "Julius Caesar";
echo
'<p>"Et tu, Brute!" exclaimed '
.
$Speaker . ".</p>";
To use escape sequences to format text:
1.
2.
Create a new document in your text editor.
Type the <!DOCTYPE> declaration, <html> element, document
head, and <body> element. Use the strict DTD and “Format-
ted Text” as the content of the <title> element.
Add the following script section to the document body:
<?php
?>
3.
4.
Declare and initialize a variable called $DisplayValue, as
follows:
$DisplayValue=9.876;
5.
Add the following PHP code to display some unformatted
text. Be sure to include the code for the opening and clos-
ing XHTML <pre> tags. Normally, the Web browser will treat
all new lines, carriage returns, and tabs as spaces. Using the
<pre> tag tells the Web browser not to convert those charac-
ters to spaces.
echo
echo
echo
echo
echo
"<pre>\n";
"Unformatted text line 1. ";
"Unformatted text line 2. ";
"$DisplayValue = $DisplayValue";
"</pre>\n";
6.
Add the following PHP code to display some formatted text:
echo
echo
echo
echo
echo
"<pre>\n";
"Formatted text line 1. \r\n";
"\tFormatted text line 2. \r\n";
"\$DisplayValue = $DisplayValue";
"</pre>\n";
Constructing
Text Strings
7.
Save
the file as FormattedText.php, upload it to the server,
and
then open the file in your Web browser by entering the
following
URL:
http://<yourserver>/PHP_Projects/Chapter.03/Chapter/
FormattedText.php.
Figure 3-5 shows the output. Notice
that
the unformatted lines run together but the formatted
lines
do not. The second formatted line is indented, and the
value
of $DisplayValue
(9.876)
appears at the beginning of
the
third line of the unformatted section. However, the text
“$DisplayValue”
appears at the beginning of the third line of
the formatted section.
131
Figure 3-5
8.
Output of FormattedText.php
Close your Web browser window.
Simple and Complex String Syntax
Values and variables can be combined in a literal string using simple
or complex syntax. Simple string syntax allows you to use the value
of a variable within a string by including the variable name inside a
text string enclosed by double quotation marks (not single quotation
marks). For example, the following code displays the text “Do you
have any broccoli?” in the Web browser:
$Vegetable = "broccoli";
echo "<p>Do you have any $Vegetable?</p>";
When the PHP scripting engine encounters a dollar sign within a
text string, it attempts to evaluate any characters that follow the dol-
lar sign as part of the variable name until it comes to a character that
is not allowed in an identifier, such as a space. With the preceding
example, the $Vegetable variable is interpreted correctly because the
question mark is not a legal character for an identifier. However, con-
sider the following version of the preceding code:
$Vegetable = "tomato";
echo "<p>Do you have any $Vegetables?</p>";
CHAPTER
3
Manipulating
Strings
132
Because
an ‘s’ is appended to the $Vegetable
variable
name, the pre-
ceding
echo
statement
displays incorrectly. The PHP scripting engine
is
attempting to locate a variable named $Vegetables
(plural),
which
has
not been declared, so no text is displayed in place of the variable
name.
To make the preceding code work, you need to surround the
variable
name with curly braces ({}),
as shown in the following exam-
ple.
This type of structure, in which variables are placed within curly
braces
inside a string, is called complex
string syntax.
$Vegetable
= "carrot";
echo
"<p>Do you have any {$Vegetable}s?</p>";
The
preceding echo
statement
displays the text string “Do you have
any
carrots?” Complex string syntax is only recognized if the opening
brace
is immediately before or after a variable’s dollar sign. The fol-
lowing
version of the preceding code also displays correctly:
$Vegetable
= "carrot";
echo
"<p>Do you have any ${Vegetable}s?</p>";
However,
if you place any characters between the opening brace and
the
dollar sign, the contents of the string are interpreted as literal
values.
For example, because the following code includes a space
between
the opening brace and the dollar sign, the echo
statement
displays
the text string “Do you have any { carrot}s?”:
$Vegetable
= "carrot";
echo
"<p>Do you have any { $Vegetable}s?</p>";
To
display a list of authors and their works:
1.
2.
Create
a new document in your text editor.
Type
the <!DOCTYPE>
declaration,
<html>
element,
document
head,
and <body>
element.
Use the strict DTD and “Books
and
Authors” as the content of the <title>
element.
Add
the following script section to the document body:
<?php
?>
3.
4.
Declare
and initialize an array called $Books,
as follows:
$Books
= array("The Adventures of Huckleberry Finn",
"Nineteen
Eighty-Four",
"Alice's Adventures in Wonderland",
"The Cat in the Hat");
5.
Declare and initialize an array called $Authors, as follows:
$Authors = array("Mark Twain",
"George Orwell",
"Lewis Carroll",
"Dr. Seuss");
Constructing
Text Strings
6.
Declare
and initialize an array called $RealNames,
as follows:
$RealNames
= array("Samuel Clemens",
"Eric
Blair",
"Charles Dodson",
"Theodor Geisel");
7.
Create a for loop to display a string that combines the values
from the three arrays, as follows. Note the use of complex
string syntax to ensure that the PHP scripting engine handles
the array elements correctly.
for ($i = 0; $i < count($Books); ++$i)
echo "<p>The real name of {$Authors[$i]}, ".
"the author of \"{$Books[$i]}\", ".
"is {$RealNames[$i]}.</p>";
133
8.
Save the file as BooksAndAuthors.php, upload it to the
server, and then open the file in your Web browser by enter-
ing the following URL:
http://<yourserver>/PHP_Projects/Chapter.03/Chapter/
BooksAndAuthors.php. Figure 3-6 shows the output in your
Web browser window.
Figure 3-6
9.
Output of the Books and Authors script
Close your Web browser window.
Short Quiz
1.
Explain the difference between a concatenation operator and
a concatenation assignment operator.
Describe two ways to display double quotation marks within a
literal string.
Describe the use of curly braces in complex string syntax.
2.
3.
CHAPTER
3
Manipulating
Strings
Working
with a Single String
PHP
provides a large number of functions for analyzing, altering, and
parsing
text strings. In this section, you will study basic techniques
for
manipulating an individual string, including how to count char-
acters
and words. You will also learn how to transpose, convert, and
change
the case of text within a string.
134
Counting
Characters and Words in a String
You
will often find it necessary to count characters and words in
strings.
For example, you might need to count characters in a pass-
word
to ensure that a user selects a password with a minimum num-
ber
of characters. Or, you might have a Web page that allows users
to
submit classified ads that cannot exceed a maximum number of
words.
The
most commonly used string-counting function is the strlen()
function,
which returns the total number of characters in a string.
You
pass to the strlen()
function
a literal string or the name of a
string
variable whose characters you want to count. For example, the
following
code uses the strlen()
function
to count the number of
characters
in a variable named $BookTitle.
The echo
statement
dis-
plays
“The book title contains 23 characters.”
$BookTitle
= "The Cask of Amontillado";
echo
"<p>The book title contains " . strlen($BookTitle)
.
" characters.</p>";
The
strlen()
function
counts
escape
sequences such as \n as
one character.
Another commonly used string-counting function is the
str_word_count() function, which returns the number of words in a
string. You pass to the str_word_count() function a literal string or
the name of a string variable whose words you want to count. The
following example shows a modified version of the preceding code,
but this time with the str_word_count() function. The echo statement
displays “The book title contains 4 words.”
$BookTitle = "The Cask of Amontillado";
echo "<p>The book title contains " .
str_word_count($BookTitle)
. " words.</p>";
To show the length and word count of some book titles:
1.
Return to the BooksAndAuthors.php script in your text
editor.
Change the content of the <title> element to “Title
Information.”
2.
Working
with a Single String
3.
4.
Delete
the $Authors
and
$RealNames
arrays.
Modify
the for
loop
to display the information about the
book
titles, as follows:
for
($i = 0; $i < count($Books); ++$i)
echo
"<p>The title \"{$Books[$i]}\" contains "
.
strlen($Books[$i])
. " characters and " .
str_word_count($Books[$i]) . " words.</p>";
135
5.
Save the file as TitleInfo.php, upload it to the server, and
then open the file in your Web browser by entering the
following URL:
http://<yourserver>/PHP_Projects/Chapter.03/Chapter/
TitleInfo.php. Figure 3-7 shows the output in your Web
browser window.
Figure 3-7
6.
Output of the Title Information script
The
count_
chars()
function
returns an
array of the 256 ASCII
codes, where the value of
each element is the
number of times that
element occurs in the
parameter string.
Close your Web browser window.
Modifying the Case of a String