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126 ” XMLReader Extension cate to subsequent if branch cases that the iterator points to a node that is within the desired table. The next if branch is entered when table row elements within the table are encountered. A combination of checking the node name and the previously set $inTable flag facilitates this. When the branch is entered, a new element in the $tableData array is initialized to an empty array. This array will later store data from cells in that row. The key associated with the row in $tableData is stored in the $row variable. Finally, the last if branch executes when table cell elements are encountered. Like the row branch, this branch checks the node name and the $inTable flag. If the check passes, it then stores the current node’s value in the array associated with the current table row. H e r e’s where the XMLREADER::END_ELEMENT node type comes into play. Once the end of the table is reached, no further data should be read into the array. So, if the ending element has the name ’table’ and the $inTable flag currently indicates that the iterator points to a node within the desired table, the flag is then set to false. Since no other tables should theoretically have the same id attribute, no if branches will execute in subsequent while loop iterations. If this table was the only one of interest in the document, it would be prudent to replace the $inTable = false; statement with a break 2; statement. This would terminate the while loop used to read nodes from the document as soon as the end of the table was encountered, preventing any further unnecessary read operations. i readString() A v a i l a b i l i t y As its entry in the PHP manual notes, the readString() method used in the above example is only present when the XMLReader extension is compiled against certain versions of the underlying libxml library. If this method is unavailable in your environment, an alternative in the example would be to have opening and closing table cell checks that toggle their ow n flag ($inCell for example) and switch cases for the TEXT and CDATA node types that check this flag and, when it is set to true, add the contents of the value property from the XMLReader instance to the $tableData array.
XMLReader Extension ” 127 DOM I n t e r o p e r a t i o n One nice feature of the XMLReader extension is the expand() method, which returns an object of the equivalent DOM extension class for the node to which the iterator currently points. Element nodes, for example, cause this method to return a DOMElement instance. The example below illustrates a modification to the previous example and provides another alternative to the readString() method for getting at the contents of table cells by taking advantage of this DOM interoperability. Closing Documents Once all necessary read operations have been conducted on a document, the close() method of the XMLReader instance should be called to cleanly terminate file access or otherwise indicate that access to the original data source is no longer needed. W r a p - U p H o p e f u l l y this chapter has given you an idea of how pull parsers work in general and when it’s better to use one like XMLReader o v e r a tree parser. F o r more information on XMLReader, check out its section in the PHP manual at http://www.php.net/manual/en/book.xmlreader.php.
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