Solution

Individual characters in strings can be referenced with array subscript
style notation, as in C. The first character in the string is at index 0.
For example:
$neighbor = ‘Hilda’;
print $neighbor[3];
d
However, PHP strings differ from C strings in that they are binary-safe
(i.e., they can contain null bytes) and can grow and shrink on
demand. Their size is limited only by the amount of memory that is
available.
You can initialize strings three ways, similar in form and behavior to
Perl and the Unix shell: with single quotes, with double quotes, and
with the “here document” (heredoc) format. With single-quoted
strings, the only special characters you need to escape inside a string
are backslash and the single quote itself:
print ‘I have gone to the store.’;
print ‘I’ve gone to the store.’;
print ‘Would you pay $1.75 for 8 ounces of tap
water?’;
print ‘In double-quoted strings, newline is
represented by \n’;
I have gone to the store.
I’ve gone to the store.
Would you pay $1.75 for 8 ounces of tap water?
In double-quoted strings, newline is represented by
\n
Because PHP doesn’t check for variable interpolation or almost any
escape sequences in single-quoted strings, defining strings this way
is straightforward and fast.
Double-quoted strings don’t recognize escaped single quotes, but
they do recognize interpolated variables and the escape sequences
shown in Table 1-1.
Table 1-1. Double-quoted string escape sequences
Escape sequence Character
\n Newline (ASCII 10)
\r Carriage return (ASCII 13)
\t Tab (ASCII 9)
\ Backslash
\$ Dollar sign
\” Double quotes
\{ Left brace
\} Right brace
\[ Left bracket
\] Right bracket
\0 through \777 Octal value
\x0 through \xFF Hex value
For example:
print “I’ve gone to the store.”;
print “The sauce cost \$10.25.”;
$cost = ‘$10.25’;
print “The sauce cost $cost.”;
print “The sauce cost \$\061\060.\x32\x35.”;
I’ve gone to the store.
The sauce cost $10.25.
The sauce cost $10.25.
The sauce cost $10.25.
The last line of code prints the price of sauce correctly because the
character 1 is ASCII code 49 decimal and 061 octal. Character 0 is
ASCII 48 decimal and 060 octal; 2 is ASCII 50 decimal and 32 hex;
and 5 is ASCII 53 decimal and 35 hex.
Heredoc-specified strings recognize all the interpolations and escapes
of double- quoted strings, but they don’t require double quotes to be
escaped. Heredocs start with <<< and a token. That token (with no
leading or trailing whitespace), followed by a semicolon to end the
statement (if necessary), ends the heredoc. For example:
print <<< END
It’s funny when signs say things like:
Original “Root” Beer
“Free” Gift
Shoes cleaned while “you” wait
or have other misquoted words.
END;
It’s funny when signs say things like:
Original “Root” Beer
“Free” Gift
Shoes cleaned while “you” wait
or have other misquoted words.
With heredocs, newlines, spacing, and quotes are all preserved. The
end-of-string identifier is usually all caps, by convention, and it is
case sensitive. Thus, this is okay:
print <<< PARSLEY
It’s easy to grow fresh:
Parsley
Chives
on your windowsill
PARSLEY;
So is this:
print <<< DOGS
If you like pets, yell out:
DOGS AND CATS ARE GREAT!
DOGS;
Heredocs are useful for printing out HTML with interpolated variables:
if ($remaining_cards > 0) {
$url = ‘/deal.php’;
$text = ‘Deal More Cards’;
} else {
$url = ‘/new-game.php’;
$text = ‘Start a New Game’;
}
print <<< HTML
There are <b>$remaining_cards</b> left.
<p>
<a href=”$url”>$text</a>
HTML;
In this case, the semicolon needs to go after the end-of-string
delimiter, to tell PHP the statement is ended. In some cases, however,
you shouldn’t use the semicolon:
$a = <<< END
Once upon a time, there was a
END
. ‘ boy!’;
print $a;
Once upon a time, there was a boy!
In this case, the expression needs to continue on the next line, so
you don’t use a semicolon. Note also that in order for PHP to
recognize the end-of-string delimiter, the . string concatenation
operator needs to go on a separate line from the end-of-string
delimiter.