passthru

Example 1098. Display the output of a random animated GIF generation script

<?php
// This script is for UNIX-like systems only

/*
    Build an animated gif from a series of randomly selected images.
    Use a directory of incrementally numbered gifs (1.gif, 2.gif, etc..) as data for the animation.
    Use the excellent package gifsicle to join the images together.
    (The gifsicle homepage is located at http://www.lcdf.org/~eddietwo/gifsicle/)
    Set up the script to allow the argument's delay and loopcount to be set from the query line.

    Note: This script can be called from an image tag. i.e:
    <a href="randimg.php?delay=1&loopcount=100" alt="This animation is a lot like a box of chocolates..." />
*/

// Send an HTTP header describing the content that will be sent by the script
header ("Content-Type: image/gif");

// Convert the delay and loopcount arguments into unsigned integers
if (is_set ($delay))
    $delay = (int) abs ($delay);

if (is_set ($loopcount))
    $loopcount = (int) abs ($loopcount);
else
    $loopcount = 'forever';

// Seed the random-number generator
mt_srand ((double) microtime () * 1000000);

// Determine how many images to use in the animation
$amount = mt_rand (4, 24);

// Find out how many images are available using a combination of UNIX shell commands
// For more information on the ls and wc commands, please check your system's man pages
$total = `ls -1 *.gif | wc -l`;
/*
    Note the backticks (`) enclosing the string in the previous instruction.
    PHP executes the contents of a backtick-delimited string as a shell command.
    Any output from the command that is sent to stdout will be returned.
*/

// Choose an image at random
while ($no_of_images--)
    $image_list[] = mt_rand (1,$total) . '.gif';

// Convert the array of images into a string of arguments for a shell command
$image_list = implode (' ', $image_list);
/*
    Note: The image names in $image_list are safe to use as shell arguments because
    they're not based on user input.
*/

// Use passthru to print the verbatim output of gifsicle
passthru("gifsicle --careful --delay $delay --loopcount=$loopcount --optimize=2 $image_list");
?>