Encyclopedia of Computer Science and Technology

372 PHPeach of the three RGB colors and thus making and combiningthree complete exposures that directly capture thecolors. This produces the best possible color accuracy but ismore expensive.The final image data is stored using a standard file format,usually JPEG (see graphics formats). The most commonlyused storage medium is an insertable “flash” memorymodule. The major competing memory card standards areCompactFlash, SD, and Sony Memory Stick. Storage capacitiesrun to 4 GB. As with regular RAM, the cost of flashmemory has declined considerably in recent years.In determining the adequacy of the camera’s storagecapacity, the user must also consider the camera’s resolution(number of pixels) and whether images will be compressedbefore storage (see data compression). While acertain amount of compression can be achieved withoutdiscernable degradation of the image, more drastic “lossy”compression sacrifices image quality for compactness. Itshould also be noted that as image resolution (and thus filesize) increases, the time needed to process and store eachimage will also increase, limiting how rapidly successiveexposures can be made.Most digital cameras have a USB connector (see USB),making it easy to upload the stored images from the camerato a PC. Once in the PC, images can be edited or otherwisemanipulated using the basic photo editing software usuallyincluded with the camera or a full-featured professionalproduct such as Adobe Photoshop.The same trends that have brought more capabilityper dollar spent on digital cameras have been even moreevident in printers (see printer). Using resolutions of2880 dots per inch or more and special papers, digitalcamera users can make prints with a quality similar tothat produced by traditional photo developers. Computerprints are more subject to color fading over time than areconventional prints, although some printer manufacturersnow offer toner that will resist fading for 25 years ormore.Future TrendsHigh-end consumer digital cameras reached the 8–10 megapixelrange by 2008, allowing for images that can be “blownup” to 10 by 12 inches or larger while retaining image qualitycomparable to conventional photos. Professional-gradedigital cameras (“digital SLRs”) are rated at 10 megapixelsor more. The need for such cameras for professional workarises not only from the higher resolution requirementsbut also because these cameras have the very high-qualityoptics used in fine 35 mm cameras, as well as having agreater variety of available specialty lenses. (Consumer digital“superzoom” cameras, however, do offer zoom lensesroughly comparable to those for low-cost 35-mm cameras.)The quality and convenience of digital photography ensurethat digital cameras will supplant conventional cameras formost consumer and many professional applications. Manydigital cameras also have the ability to shoot short videosequences. The ubiquity of digital cameras and digital video(even in many cell phones) has had important social consequencesby facilitating transmission of pictures of disasters,political gaffes, and other events often outside the mainstreammedia (see user-created content and YouTube).Digital camcorders will also become more widely used.Their resolution is generally from about a quarter millionpixels to a million pixels—considerably lower than fordigital still cameras, but adequate and likely to improve.Digital video cameras are also rated according to lux value,indicating the minimum light level for satisfactory recording.Most digital videos store the captured image to tape(either MiniDV or Hi-8), but some newer cameras use builtinrecordable DVD disks instead (see CD-Rom and DVD-ROM). The ability to digitally edit video direct from thecamera is also an important advantage.Further ReadingBusch, David D. Digital SLR Cameras & Photography for Dummies.2nd ed. Hoboken, N.J.: Wiley, 2007.Etchells, Dave. “Finding the Right Digital Camera.” ImagingResource Newsletter. Available online. URL: http://www.imaging-resource.com /TIPS/ BUYGD/ BUYGUID.HTM.Accessed August 17, 2007.King, Julie Adair. Digital Photography for Dummies. 5th ed. Hoboken,N.J.: Wiley, 2005.Silva, Robert. “Digital Camcorder Formats.” Available online. URL:http://hometheater.about.com/od/camcorders/a/camformats_2.htm. Accessed August 17, 2007.Wilson, Tracy V., K. Nice, and G. Gurevich. “How Digital CamerasWork.” Available online. URL: http://www.howstuffworks.com/digital-camera.htm. Accessed August 17, 2007.PHPPHP is a very popular scripting language primarily usedfor creating dynamic Web pages (see Ajax and scriptinglanguages). PHP originated in 1994 as a way for Danishprogrammer Rasmus Lerdorf to replace a set of Perl scriptsused to manage his own Web page—hence the originalname “personal home page.” Lerdorf released the first versiontogether with a “form interpreter” in 1995. In 1997 thelanguage parser was rewritten by Israeli developers ZeevSuraski and Andi Gutmans, who launched PHP3 in 1998;since then the initials PHP have (recursively) stood for PHP:Hypertext Processor. In 2004 the current version, PHP5,was released. As the language has evolved, it has improvedin its support for objects (see object-oriented programming)as well as in its connectivity to MySQL and otherdatabase and Web-application coordination technologies.PHP normally runs on a Web server and processes PHPcode, which is often embedded within Web pages (seeHTML). The classic Hello World program would look likethis:The PHP processor parses only the code within the delimiters. (An alternative set of delimiters is .Besides being embedded in HTML pages, PHP canbe used interactively at the command line, where it hasreplaced older languages such as awk, Perl, or shell script-