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DOMXPath::evaluate

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

DOMXPath::evaluate Avalia a expressão XPath fornecida e retorna um resultado tipado se possível

Descrição

public DOMXPath::evaluate(string $expression, ?DOMNode $contextNode = null, bool $registerNodeNS = true): mixed

Executa a expressão XPath expression fornecida e retorna um resultado tipado se possível.

Parâmetros

expression

A 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.

registerNodeNS

Define 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.

Valor Retornado

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.

Exemplos

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

Veja Também

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User Contributed Notes 5 notes

up
4
daniel at danielnorton dot com
12 years ago
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.
up
4
Damien Bezborodov
12 years ago
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])".
up
4
yuriucsal at NOSPAM dot yahoo dot com dot br
19 years ago
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

}
}
}
?>
up
1
aazaharov81 at gmail dot com
9 years ago
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'));
?>
up
1
danny at webdevelopers dot eu
4 years ago
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);
}
?>
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