![]() ![]() * For things like result set iterators, there really isn't always a "key" that you can return, unless you know you have a scalar primary key column in the query. I do this by explicitly calling next() from the end of my rewind() implementation. ![]() * Make sure your rewind() implementation tries to grab the first result so that the subsequent call to valid() will know whether or not the result set is empty. Otherwise your code will break if the same iterator is used in two consecutive foreach loops when the first loop terminates with a break statement before all the results are iterated over. * Make sure you close your cursor or otherwise clean up any previous query at the top of the rewind method. Things to keep in mind when making a database result set iterator: Iterator::rewind() method isn't called until then. In this case, the construction of the iterator itself can be cheap, and after construction you can continue to set the properties of the query all the way up to the beginning of the foreach loop since the If your iterator is doing something expensive, like making a database query and iterating over the result set, the best place to make the query is probably in the Iterator::rewind() implementation. On the other hand, sometimes it is convenient for this method to return something, in which case you can do so if you want. The Iterator::next() method need not return anything. The only two methods that are always executed are Iterator::rewind() and Iterator::valid() (unless rewind throws an exception). The loop isn't terminated until Iterator::valid() returns false or the body of the loop executes a break statement. After each iteration of the loop, Iterator::next() is called and we repeat from step 2 above. If Iterator::valid() returns true, Iterator::current() andĥ. It Iterator::valid() returns false, the loop is terminated.ģb. Before each iteration of the loop, Iterator::valid() is called.ģa. Before the first iteration of the loop, Iterator::rewind() is called.Ģ. Order of operations when using a foreach loop:ġ. The while statement will loops through a block of code as long as the condition specified in the while statement evaluate to true.Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Predefined Attributes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto search ![]() The foreach() loop work specifically with arrays. You will also learn how to loop through the values of array using foreach() loop at the end of this chapter.
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