Variable Types
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| Variable Types |
Integers
An integer is any numeric value that does not have a decimal point, such as the following:
• 5 (five)
• –5 (negative five)
• 0123 (preceded by a zero; octal representation of decimal number 83)
• 0x12 (preceded by 0x; hexadecimal representation of decimal number 18)
Floating-Point Numbers
A floating-point number (commonly referred to simply as a float or double, which, in PHP, are exactly the same thing) is a numeric value with a decimal point.
The following are all floating-point values:
• 5.5
• .055e2 (scientific notation for .055 times 10 to the second power, which is 5.5)
• 19.99
The second example is a float represented in scientific notation. The e, as is often the case on graphing calculators, means “times 10 to the”. It is followed by whatever power 10 should be raised to in order to put the decimal wherever you want it. Thus, .055e2 is the same as .055 times 100, which is 5.5.
Arrays
ARRAY INDEXING
The following example demonstrates the construction of an array containing
five names, then printing each name on a separate line:
<?php
/* ch02ex03.php – demonstration of arrays */
$namesArray = Array(‘Joe’, ‘Bob’, ‘Sarah’, ‘Bill’, ‘Suzy’);
echo “$namesArray[0]<br>”;
echo “$namesArray[1]<br>”;
echo “$namesArray[2]<br>”;
echo “$namesArray[3]<br>”;
echo “$namesArray[4]<br>”;
?>
NOTE : The <br> tags are given here to separate each element of the array on a separate line.
The following example demonstrates the use of empty brackets after an
array to add new elements and also explicitly defines a certain element in
an array:
$namesArray = Array(‘Joe’, ‘Bob’, ‘Sarah’, ‘Bill’, ‘Suzy’);
$namesArray[] = ‘Rachel’; // adds ‘Rachel’ as $namesArray[5]
$namesArray[3] = ‘John’; // replaces ‘Bill’ with ‘John’
Strings
Single-quoted strings are always interpreted just as they are. For example, to use “My variable is called $myVariable” as a string, use the statement found in the following example:
/* ch02ex04.php – shows use of single-quoted strings */
echo ‘My variable is called $myVariable’;
?>
The output from this example is
My variable is called $myVariable
As you may have noticed from the echo statements found earlier in this
chapter, double-quoted strings are interpreted so that variables are
expanded before they are actually stored as a value. Consider the following
example:
<?php
/* ch02ex05.php – shows use of double-quoted strings */
// Do single-quote assignment and output result
$myVariable = ‘My variable is called $myVariable’;
echo $myVariable;
// Move to new line
echo ‘<br>’;
// Do double-quote assignment and output result
$myVariable = “My variable is called $myVariable”;echo $myVariable;
?>
The output from this example is :
My variable is called $myVariable
My variable is called My variable is called $myVariable
CHARACTER ESCAPING
and its contents surrounded by quotes inside the string $strBig:
<?php
/* ch02ex06.php – demonstrates character escaping */
$strSmall = “John Smith”;
$strBig = “The name stored in \$strSmall is \”$strSmall\”.”;
echo $strBig;
?>
Thus, the output of the above program is
The name stored in $strSmall is “John Smith”.
STRING INDEXING
$string{index}
For example, take a look at the following program:
<?php
/* ch02ex07.php – demonstrates string indexing */
// Assign a name to $strName
$strName = “Walter Smith”;
// Output the fifth letter of the name
echo $strName{4};
?>
Objects
Objects are a powerful method of program organization. They are essentially what people are talking about when they refer to OOP or Object- Oriented Programming. Objects (and their definitions, called classes) are discussed in depth in Chapter 12, “Using Include Files (Local and Remote).”
