CHAPTER
3
Manipulating
Strings
126
When
you want to include single quotes within a literal string, the
easiest
method is to surround the literal string with double quotation
marks.
Likewise, to include double quotes within a literal string, you
can
surround the string with single quotation marks. For example, the
following
statement assigns a text string surrounded by double quota-
tion
marks to the $LatinQuote
variable.
Figure 3-2 shows the output
of
the echo
statement.
$LatinQuote
= '<p>"Et tu, Brute!"</p>';
echo
$LatinQuote;
Figure
3-2
Displaying
a string that contains double quotation marks
Later
in this chapter, you will learn other methods to include quota-
tion
marks and other special characters in text strings.
Working
with String Operators
Up
to this point, you have displayed values from multiple literal
strings
and variables by passing them to the echo
and
print
state-
ments
as multiple arguments separated by commas. For example, the
following
code passes two literal strings and a variable to the echo
statement:
$Speaker
= "Julius Caesar";
echo
'<p>"Et tu, Brute!", exclaimed ', $Speaker, ".</p>";
of
these operators is the concatenation
operator (.).
The following
code
uses the concatenation operator to combine several string vari-
ables
and literal strings, and assigns the new value to another variable:
$City
= "Paris";
$Country
= "France";
$Destination
= "<p>" . $City . " is in "
.
$Country . ".</p>";In php, you can also use two operators to combine strings. The first
echo $Destination;
Constructing
Text Strings
The
combined value of the $City
and
$Country
variables
and the
literal
strings that are assigned to the $Destination
variable
is
<p>Paris
is in France.</p>.
You
can also combine strings using the concatenation
assignment
operator
(.=).
The following code combines two text strings, but
without
using the $City
or
$Country
variables:
$Destination
= "<p>Paris";
$Destination
.= " is in France.</p>";
echo
$Destination;
127
Again,
the value of the $Destination
variable
is "<p>Paris
is in
France.</p>".
To
build a string using the concatenation assignment operator:
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 “Musical
Scale”
as the content of the <title>
element.
Add
the following script section to the document body:
<?php
?>
3.
4.
Insert
the following array in the script section:
$MusicalScale
= array("do", "re", "mi", "fa",
"so",
"la",
"ti");
5.
Build
an output string using a foreach
loop
with the
$MusicalNotes
array,
as follows:
$OutputString="The
notes of the musical scale are: ";
foreach
($MusicalScale as $CurrentNote)
$OutputString
.= " " . $CurrentNote;
6.
Add the following statements to display the results in your
browser window.
echo "<p>$OutputString</p>";
7.
Save the file as MusicalScale.php, upload it to the Chap-
ter folder for Chapter 3, and then open the file in your Web
browser by entering the following URL:
http://<yourserver>/PHP_Projects/Chapter.03/Chapter/
MusicalScale.php. Figure 3-3 shows the output.
CHAPTER
3
Manipulating
Strings
128
Figure
3-3
Output
of MusicalScale.php
8.
Close
your Web browser window.
Adding
Escape Characters and Sequences
You
need to take extra care when using single quotation marks with
possessives
and contractions in strings surrounded by single quota-
tion
marks because the PHP scripting engine always looks for the first
closing
single quotation mark to match an opening single quotation
mark.
For example, consider the following statement:
echo
'<p>This code's not going to work.</p>';
This
statement displays incorrectly because the PHP scripting engine
assumes
that the literal string ends with the apostrophe following “code.”
To
get around this problem, you should include an escape character
before
the apostrophe in “code’s”. An escape
character tells
the compiler
or
interpreter that the character that follows it has a special
purpose.
In
PHP, the escape character is the backslash (\).
Placing a backslash in
front
of an apostrophe tells the PHP scripting engine to treat the apos-
trophe
as a regular keyboard character, such as “a,” “b,” “1,”
or “2,” and not
as
part of a single quotation mark pair that encloses a text string.
The
backslash
in the following statement tells the PHP scripting engine to
display
the apostrophe following the word “code” as an apostrophe:
echo
'<p>This code\'s going to work.</p>';
There’s
no need for a backslash before an apostrophe if you surround
the
text string with double quotation marks, as follows:
echo
"<p>This code's going to work.</p>";
Although
the apostrophe in the preceding statement displays cor-
rectly,
other characters require an escape character within a string
surrounded
by double quotation marks. The escape character
combined
with one or more other characters is called an escape
sequence.
The backslash followed by an apostrophe (\')
is an exam-
ple
of an escape sequence. Most escape sequences carry out special
functions;
for example, the escape sequence \t
inserts
a tab into a
string.
Table 3-1 describes the escape sequences that can be added to
a
double-quoted string in PHP.
Constructing
Text Strings
Escape
Sequence
\\
\$
\r
\f
\"
\t
\v
\n
\xh
\o
Within
a
literal string
surrounded
by double
quotation
marks, the backslash will
be displayed if you place
it before any character
other than those listed in
Table 3-1.
Description
Inserts a backslash
Inserts a dollar sign
Inserts a carriage return
Inserts a form feed
Inserts a double quotation mark
Inserts a horizontal tab
Inserts a vertical tab
Inserts a new line
Inserts a character whose hexadecimal value is h, where h is
one or two hexadecimal digits (0-9, A-F), case insensitive
Inserts a character whose octal value is o, where o is one,
two, or three octal digits (0-7)
PHP escape sequences within double quotation marks
129
Table 3-1
Notice that the backslash is one of the characters inserted into a
string by an escape sequence. Because the escape character itself
is a backslash, you must use the escape sequence \\ to include a
backslash as a character in a string. For example, to include the path
“C:\Course Technology\1687-5\” in a string, you must include a
backslash escape character before every literal backslash you want
to appear in the string, making each single backslash into a pair of
backslashes:
echo "<p>My PHP files are located in
C:\\Course Technology\\1687-5\\.</p>";
As a good
programming
practice, you
should include
an \n escape
sequence at the end of
an echo statement out-
put string as needed to
properly format the