(PHP 5 >= 5.1.0, PHP 7, PHP 8)
DOMXPath::evaluate — Avalia a expressão XPath fornecida e retorna um resultado tipado se possível
$expression, ?DOMNode $contextNode = null, bool $registerNodeNS = true): mixed
Executa a expressão XPath expression fornecida e retorna
um resultado tipado se possível.
expressionA expressão XPath a ser executada.
contextNode
O contextNode opcional pode ser especificado para
realizar consultas XPath relativas. Por padrão, as consultas são relativas ao
elemento raiz.
registerNodeNSDefine se deve-se registrar automaticamente os prefixos de espaços de nomes dentro do escopo no nó de contexto para o objeto DOMXPath. Isto pode ser usado para evitar a necessidade de se chamar DOMXPath::registerNamespace() manuallmente para cada espaço de nome dentro do escopo. Quando existir um conflito entre prefixos de espaços de nomes, apenas o prefixo do espaço de nome descendente mais próximo será registrado.
Retorna um resultado tipado se possível ou uma DOMNodeList
contendo todos os nós que correspondem à expressão XPath expression.
Se a expression estiver malformada ou o
contextNode for inválido,
DOMXPath::evaluate() retorna false.
Exemplo #1 Obtendo a contagem de todos os livros em inglês
<?php
$doc = new DOMDocument;
$doc->load('book.xml');
$xpath = new DOMXPath($doc);
$tbody = $doc->getElementsByTagName('tbody')->item(0);
// nossa consulta é relativa ao nó tbody
$query = 'count(row/entry[. = "en"])';
$entries = $xpath->evaluate($query, $tbody);
echo "There are $entries english books\n";
?>O exemplo acima produzirá:
There are 2 english books
Note that this method does not provide any means to distinguish between a successful result that returns FALSE and an error.
For example, this will succeed and return FALSE:
<?php $xpath->evaluate("1 = 0"); ?>
One workaround when you know you are expecting a Boolean is to wrap the result with string(). e.g.
<?php $xpath->evaluate("string(1 = 0)"); ?>
This will return a string "false" on success, or the Boolean FALSE on error.If your expression returns a node set, you will get a DOMNodeList instead of a typed result. Instead, try modifying your expression from "//node[1]" to "string(//node[1])".this class can substitute the method evaluate while it is not validated. Made for Yuri Bastos and Jo�o Gilberto Magalh�es.
<?php
class XPtahQuery
{
// function returns a DOMNodeList from a relative xPath
public static function selectNodes($pNode, $xPath)
{
$pos = strpos(self::getFullXpath($pNode),"/",1);
$xPathQuery = substr(self::getFullXpath($pNode),$pos);//to paste /#document[1]/
$xPathQueryFull = $xPathQuery. $xPath;
$domXPath = new DOMXPath($pNode->ownerDocument);
$rNodeList = $domXPath->query($xPathQueryFull);
return $rNodeList;
}
// function returns a DOMNode from a xPath from other DOMNode
public static function selectSingleNode($pNode, $xPath)
{
$pos = strpos(self::getFullXpath($pNode),"/",1);
$xPathQuery = substr(self::getFullXpath($pNode),$pos);//to paste /#document[1]/
$xPathQueryFull = $xPathQuery. $xPath;
$domXPath = new DOMXPath($pNode->ownerDocument);
$rNode = $domXPath->query($xPathQueryFull)->item(0);
return $rNode;
}
//utilitaries functions off selectSingleNode
private function getNodePos($pNode, $nodeName)
{
if($pNode == null)
{
return 0;
}
else
{
$var = 0;
if ($pNode->previousSibling != null)
{
if ($pNode->previousSibling->nodeName == $nodeName)
{
$var = 1;
}
}
return self::getNodePos($pNode->previousSibling, $nodeName) + $var;
}
}
//utilitaries functions off selectSingleNode
private function getFullXpath($pNode)
{
if($pNode == null)
{
return "";
}
else
{
return self::getFullXpath($pNode->parentNode) . "/" . $pNode->nodeName . "[" .strval(self::getNodePos($pNode, $pNode->nodeName)+1) . "]";//+1 to get the real xPath index
}
}
}
?>To query DOMNodes by their HTML classes, use such snippet
<?php
// CssClassXPathSelector
function ccxs($class) {
return '[contains(concat(" ", normalize-space(@class), " "), " ' . $class . ' ")]';
}
// then just
$domitems = $this->xpath("//*[@id='searchResultsRows']//a" . ccxs('listing_row'));
?>The only way how to distinguish FALSE returned value from syntax error FALSE is to re-run the XPath expression wrapped in string() function. If must return empty string. If it returns FALSE again then it is an error.
<?php
$ret=$this->xp->evaluate($eval, $context);
// Error detection: DOMXPath::evaluate() returns FALSE on error
// so does DOMXPath::evaluate("boolean(/nothing)")
// @workaround webdevelopers.eu
if ($ret === false && $this->xp->evaluate("string($eval)", $context) === false) {
throw new Exception("Invalid XPath expression ".json_encode($eval), 3491);
}
?>