PHP Programming
Variables

Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.[php.net]

Variables are used to store strings, numbers and arrays.

$class = "Web Design";

$period = 4;

$students = array("Mary" , "Bill" , "Terry" , "Leslie" , "Joe");

$grade_asn1 = array('Mary' => 'A' , 'Bill' => 'B' , 'Terry' => 'C' , 'Leslie' => 'B' , 'Joe' => 'A');

$class is a string variable.
$period is a number variable. A number variable may be an integer, such as 4, or a floating point number (also known as "float", "double", or "real number"), such as 4.5.
$students is an integer indexed array. The first item (Mary) in the array is at index zero. Note that arrays are declared with the array() function and values are separated by commas (,). An array value is accessed by placing the index number, or key, in square braces [ ] following the variable name, e.g., $students[2] returns the value "Terry".
$grade_asn1 is an associative array. The first item in this array is at index, or key, Mary and this is associated with the value 'A', e.g., $grade_asn1["Leslie"] returns the value "B". This association is often referred to as key => value.

Notes:

Each code line in PHP must end with a semicolon (;).
PHP may be embedded anywhere within the document. A block of PHP starts with <?php and ends with ?>
PHP files must have an extension of php, e.g., index.php. The php file extension tells the server that this file must be sent to the PHP processor before it is sent to the user. The PHP processor executes, then removes, all PHP code and sends only HTML to the user.

Let's put it all together in a short php program:

<!doctype html public "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Web Design Assignment #1 Grades </title>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
</head>
<body>
<?php
$class = "Web Design";
$period = 4;
$students = array("Mary" , "Bill" , "Terry" , "Leslie" , "Joe");
$grade_asn1 = array('Mary' => 'A' , 'Bill' => 'B' , 'Terry' => 'C' , 'Leslie' => 'B' , 'Joe' => 'A');
?>
<h1><?php echo"$class"; ?></h1>
<?php
echo"<p>Period $period</p>";
echo"<p>Assignment #1 Grades</p>";
for($i=0;$i<5;$i++)
{
$student = $students[$i];
echo"<p>$student Grade $grade_asn1[$student]</p>";
}
?>
</body>
</html>

The "for" loop is used to iterate through the values in $students (student names). The "for" loop has three parameters (Initial condition, $i=0 ; Continue when True, $i<5 ; Increment the initial condition, $i++). The script contained within the curly-braces { } is executed for each cycle. In this case, the value of $i is different each time through the cycle. This results in the array $students[$i] assigning a different student name to $student each cycle. The value of $student is used as the key in $grade_asn1[$student] which contains the grade (value) associated with each student.

Here is what is displayed in the browser:

Web Design

Period 4

Assignment #1 Grades

Mary Grade A

Bill Grade B

Terry Grade C

Leslie Grade B

Joe Grade A

Adding to Variables

String Variables

Strings are concatenated (joined) with the dot (.). For example, if we have three string variables,
$string1 = "Alien"
$string2 = "Ant"
$string3 = "Farm"
we can join the strings, separated with spaces, into a single variable, as follows:
$string4 = $string1." ".$string2 . " " . $string3 (Note that white space on either side of the dot is ignored.)
If we echo, or print, $string4 we will see,
Alien Ant Farm

Number Variables

Number variables are added with the plus sign (+). For example, if we have two numeric variables,
$x = 5
$y = 2
we can add the two variables and assign the result to a new variable,
$z = $x + $y
If we echo, or print, $z we will see,
7

Operators and Control Structure

IF Construct

Back to HTML Tools

PHP ProgrammingVariables

Web Design

Adding to Variables

String Variables

Number Variables

PHP Programming
Variables