Networks & Transactions 1

Monday, January 23

Lab concepts:

Connecting to the server (Ernie)
Using the text editor (TextWrangler)
PHP on the server, HTML in the browser
The command line (Terminal and the Unix shell)
Statements are executed in strict order
Displaying text
Variables
Passing command-line arguments (parameters) to your program
Control structures: if...else conditions, do...while iteration loops

Lab corresponds to:

Boudreaux pp 34-55, but for now we are outputting regular text from PHP to use at the

command line, not HTML for use in a web browser-- a key point of disparity between this lab and the book. Also (for the same reason), the book doesn't discuss passing command-line arguments as input to your program.

1-hello.php

<?php

// ------ FIGURE OUT THE COMMAND LINE ARGUMENTS

// $argc is the count of arguments that were passed, including the filename.
// So the command "php 1-hello.php Kate 30", there are 3 arguments (1-hello.php, Kate, and 30)

// Exit with an error message if the user supplied less than the 3 required arguments

if ($argc < 3) exit("Please enter username and age, like this: php hello.php Kate 30\n\n");

// $argv is an array containing the arguments that were passed, including the filename
// $argv[0] is the filename, $argv[1] is the first argument after that, $argv[2] is the second argument, etc.

// Assign the argument values to more meaningfully named variables

$userName = $argv[1];
$age = $argv[2];

// ------ GREET THE USER

// Echo displays some text. The parentheses () are optional for echo.
// Variable names can be included in the text, and echo will then substitute the variable contents.
// For a newline, use the special combination \n

echo("Hello $userName\n\n");
echo("Age: $age\n\n");

// This is variable assignment. We are computing the result of $age * 2, and assigning that value to $differentAge.

$differentAge = $age * 2;
echo("Twice my age: $differentAge\n\n");

// Conditional. Everything between the {} will be executed only if the condition ($age < 75) is TRUE.

if ($age < 75) {
echo("Not too old\n\n");
echo("You are a young 'un\n");
}

// Else. Everything between this {} will be executed only if the above condition ($age < 75) was NOT true.

else {
echo("Old\n\n");
}

// ------ DISPLAY A COUNT FROM ONE THROUGH THE AGE

// Initialize a counter variable

$count = 1;

// This is a "do...while" loop. Everything between the {} will be executed repeatedly, UNTIL the "while" condition is NOT true.
do {

// Display the count so far

echo("$count ");

// Add one to the count. This is just assignment again-- see "$differentAge = $age * 2".
// We compute the result of $count + 1, then assign that value back into $count, overwriting the previous value.

$count = $count + 1;

// Do a nested loop to display 10 periods.
// Notice how this whole inner loop of 10 periods happens every time we pass through the outer loop.
// For example, "$count = 1" happens only once, but if $age is 30, then "$innerCount = 1" will eventually happen 30 times.

$innerCount = 1;
do {
echo(".");
$innerCount = $innerCount + 1;
} while ($innerCount <= 10);

// After the inner loop of 10 periods is done, display one space

echo(" ");

} while ($count <= $age);

// See also "while" loops (the condition is evaluated at the beginning instead of the end), and "for" loops.

// After the outer loop is done, display a message and two newlines

echo("Done!\n\n");

?>

Lab1