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CopyrightIBMCorporation2010TrademarksSimulateXQueryandXIncludefunctionalitywithPHPPage1of8SimulateXQueryandXIncludefunctionalitywithPHPEnjoythepowerofXMLdataprocessinginwebprogrammingColinBeckinghamSeptember21,2010ManybrowserscanhandleXMLingeneral,butarecurrentlyweakintheirsupportofXQueryandXInclude.
YouneedtoworkaroundthisissuewhenyoubuildwebapplicationsthatcombineandprocessXML-structureddatafrommultiplesources.
UsingPHPisonesolution.
ThisarticlefirstshowshowyourwebpagescandeliverdataextractsfromXMLusingXQueryandXIncludeexplicitly,andthenhowtodotheequivalentworkwithPHP,allwithinthecontextofacooperativeeffortamonggardencenters.
XIncludeandXQueryareXMLtoolsthathelpwebprogrammersprocessdatadynamically.
XIncludeletsyoutreatmultipleXMLfilesasiftheywereonefile,andXQuerycanprocessthecombineddataandprepareitforinclusionintooutputforweb-pagedisplay.
Together,theyperformthisserviceelegantlyandefficientlywithfewlinesofcode.
FrequentlyusedacronymsHTTP:HypertextTransferProtocolW3C:WorldWideWebConsortiumXHTML:ExtensibleHypertextMarkupLanguageXML:ExtensibleMarkupLanguageXSL:ExtensibleStylesheetLanguageMostbrowserscandisplayandprocessXMLfileseitherdirectlyorincooperationwithXSLtemplates.
Inanidealworld,browserswouldunderstandXQueryandXIncludedirectlytoo.
Butatthispointtheysupportthesetoolsonlybyplacingunreasonabledemandsonusers—forexample,byrequiringthemtoloadexperimentaladd-ons.
Fetchingthedatafromwidelydifferentsourcesandcombiningthemintoonelargedatasetforprocessingcanbeapainstakingtaskforthewebprogrammer.
Throughahypotheticalbusinessexample,thisarticlefirstshowsyouthestrengthofthecombinationofXQueryandXInclude.
Thenyou'lllearnhowtousePHPtosimulatethefunctionalitythatXQueryandXIncludeprovide.
MovingallthedataprocessingtotheserversidegivesyouaworkaroundtolimitedbrowsersupportforXQueryandXInclude.
AnotherbenefitisthatPHPgivesyoumuchfinercontroloverthefinaloutputpresentation.
developerWorksibm.
com/developerWorks/SimulateXQueryandXIncludefunctionalitywithPHPPage2of8Example:Garden-centercooperationImaginethatatownhasthreegardencenters.
Theycompetewithoneanotherbutprovidesufficientlydifferentservicesthattheycandosocooperativelyratherthanantagonistically.
Theydosomemarketresearchtogetfindouthowtheircustomersbuytheirplants.
Inthehorticulturebusiness,salesofhighlyperishableproductsoccurinhighvolumeinashortperiodoftime,andcustomerscanbequiteparticularaboutthetypeandqualityofproductstheywant.
Itisinthebestinterestofthebusinesstogetthehigh-maintenanceproducts(forexample,thosethatneedtobewateredandkeptfreeofpests)outthedoorassoonaspossibleandtokeepamercurialcustomerbasehappybyprovidingthemwiththerightproductsattherighttimeandintherightplace.
Otherwisecustomersflocktothecompetitionthatcan.
Researchshowsthatcustomersdonotlikephoningaroundtofindwheretheycangettheirplants,andthehighvolumeofcallsisinconvenienttothebusinessesaswell.
Atthebeginningoftheseason,allthebusinesseshaveplentyofproduct.
Laterintheseason,despitegoodplanning,productstartstorunoutunevenly.
Customerslookingforpetuniasmighthavetophoneorvisitallthreegardencentersbeforetheyfindthehotpinkcolorthey'relookingfor.
Ingeneral,customerswanttoknowwhohaswhichplant,inwhatsizepot,inwhatquantity,andatwhatprice.
TheproposedsetupThethreeITmanagersholdameeting.
Theydecidetocreateacommonwebsitewherecustomerscanfindoutwhichgardencenterhasspecificplantsinstock.
Althoughallthreegardencentersarecomputerized,eachusesadifferentsystemtostoreinformation.
ApplesandThingsusesaMicrosoftAccessdatabasesystem,BirchTreesUnlimitedusesaLinuxsystemwithMySQL,andCarnationTarnationusesMacOSXwithIBMDB2.
Broadly,theydecidetoworktowardanXML-basedarchitecture.
XMLisaconvenientdataformatbecauseeachoftheirsystemscanexportcurrentdatatoanXMLfilethatisavailableinthecloud.
AmasterXMLfilecollectstheindividualstores'dataintoonecentralplace,usingXInclude.
Finally,themainwebpageexaminesthemasterfile,extractsthedatausingXQuery,andrendersthefinaldisplay.
ProcessingtheXMLwithXIncludeandXQueryTheITmanagersdecidethateachstorewillproduceanXMLfilesimilartotheoneinListing1:Listing1.
StoreXMLfile.
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ibm.
com/developerWorks/developerWorksSimulateXQueryandXIncludefunctionalitywithPHPPage3of8PetuniaPink,in4inchpots1003.
00Appletree'Spartan'625.
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Thisfilehasastorerootelementandtwochildelements.
Theinfochildelementcontainsinformationaboutthestoreingeneral.
Theplantschildelementcontainsmanyplantchildelements,eachofwhichcontainsfurtherinformationaboutthatplant,includingthename,description,quantityandprice.
Allthreestoresfollowthispatternexactly.
Listing2istheirversionofamainXMLfilethatcombinesallthreestorefilessotheyappeartobeonelargefile,maintainingdetailsabouttheproducts:Listing2.
MainXMLfileInListing2,XIncludeisusedtofetchdatafromthethreelocationsusingHTTPinthecloud.
Afterprocessing,itlookslikeListing3:Listing3.
MainXMLfileexpandedApples.
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Birches.
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developerWorksibm.
com/developerWorks/SimulateXQueryandXIncludefunctionalitywithPHPPage4of8InListing3,theincludeinstructionsfromListing2arereplacedbythecontentsoftheindividualstoreXMLfiles.
EachstoreelementisnowachildelementoftheglobalstoreDataelement.
YoucannowapplyXQuerytothecombineddataset,asinListing4:Listing4.
ApplyingXQuery{for$storeindoc("mainXMLfile.
xml")/storeData/storelet$plants:=$store/plants/plantreturn{for$plantin$plantsorderby$plant/namereturn{concat($plant/quantity,"of",$plant/name,"at",$store/info/name,"for",$plant/price,"each")}