Displaying Validation WarningsEnforcing Data RulesHighlighting Fields That Require AttentionSummaryLesson 14. Cookies and SessionsCookiesSessionsSummaryLesson 15. User AuthenticationTypes of AuthenticationBuilding an Authentication SystemSummaryLesson 16. Communicating with the Web ServerHTTP HeadersServer Environment VariablesSummaryLesson 17. Filesystem AccessManaging FilesReading and Writing FilesSummaryLesson 18. Host Program ExecutionExecuting Host ProgramsThe Host EnvironmentSecurity ConsiderationsSummaryLesson 19. Using a MySQL DatabaseUsing MySQLExecuting SQL StatementsDebugging SQLSummaryLesson 20. Database AbstractionThe PEAR DB ClassDatabase Portability IssuesSummaryLesson 21. Running PHP on the Command LineThe Command-Line EnvironmentWriting Scripts for the Command LineSummaryLesson 22. Error HandlingError ReportingSummaryLesson 23. PHP ConfigurationConfiguration SettingsConfiguration DirectivesLoadable ModulesSummaryLesson 24. PHP SecuritySafe ModeOther Security FeaturesSummaryLesson 25. Using PEARIntroducing PEARUsing PEARSummaryAppendix A. Installing PHPLinux/Unix InstallationWindows InstallationTroubleshooting