Page 106 - Beginning PHP 5.3

Part II: Learning the Language

Figure 4-4

How It Works
This script uses a number of decisions and loops to simulate the pigeon flying toward home and
displays the results.
First, the script displays an XHTML page header. Then it sets a variable, $mapSize, representing the
width and height of the map square (you might want to try experimenting with different values to see
how it affects the simulation):

$mapSize = 10;

Next, you encounter the first loop of the script: a do...while loop. This code uses PHP’s rand()
function to randomly position the home point and the pigeon within the boundaries of the map. After
positioning the home and pigeon, the condition of the do...while loop checks to ensure that the
home and the pigeon are at least half the width (or height) of the map apart from each other; if they’re
not, the loop repeats itself with new random positions. This ensures that the pigeon always has a
reasonable distance to travel:
// Position the home and the pigeon
do {
$homeX = rand ( 0, $mapSize-1 );
$homeY = rand ( 0, $mapSize-1 );
$pigeonX = rand ( 0, $mapSize-1 );
$pigeonY = rand ( 0, $mapSize-1 );
} while ( ( abs( $homeX - $pigeonX ) < $mapSize/2 ) && ( abs( $homeY -
$pigeonY ) < $mapSize/2 ) );

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