如何在XPath评估之前处理字符串中的双引号?

时间:2011-01-27 18:04:00

标签: php string xpath quotes xpath-1.0

在下面的函数中,当$ keyword中的字符串包含双引号时,它会创建一个“警告:DOMXPath :: evaluate():无效的表达式”

$keyword = 'This is "causing" an error';
$xPath->evaluate('boolean(//img[contains(@alt, "'.$keyword.'")])');

如何为评估xpath表达式准备$keyword

完整的功能代码:

$keyword = trim(strtolower(rseo_getKeyword($post)));

function sx_function($heading, $post){
    $content = $post->post_content;
    if($content=="" || !class_exists('DOMDocument')) return false;
    $keyword = trim(strtolower(rseo_getKeyword($post)));
    @$dom = new DOMDocument;
    @$dom->loadHTML(strtolower($post->post_content));
    $xPath = new DOMXPath(@$dom);
    switch ($heading)
        {
        case "img-alt": return $xPath->evaluate('boolean(//img[contains(@alt, "'.$keyword.'")])');
        default: return $xPath->evaluate('boolean(/html/body//'.$heading.'[contains(.,"'.$keyword.'")])');
        }
}   

2 个答案:

答案 0 :(得分:6)

PHP具有Xpath 1.0,如果您有一个带双引号和单引号的字符串,则解决方法是使用Xpath concat()函数。辅助函数可以决定何时使用什么。实施例/用法:

xpath_string('I lowe "double" quotes.');
// xpath:    'I lowe "double" quotes.'

xpath_string('It\'s my life.');
// xpath:    "It's my life."

xpath_string('Say: "Hello\'sen".');
// xpath:    concat('Say: "Hello', "'", "'sen".')

辅助函数:

/**
 * xpath string handling xpath 1.0 "quoting"
 *
 * @param string $input
 * @return string
 */
function xpath_string($input) {

    if (false === strpos($input, "'")) {
        return "'$input'";
    }

    if (false === strpos($input, '"')) {
        return "\"$input\"";
    }

    return "concat('" . strtr($input, array("'" => '\', "\'", \'')) . "')";
}

答案 1 :(得分:4)

要转义XPath 2.0 string literals中的字符串分隔符,您需要将每个分隔符替换为2,因此"需要替换为""

[74]      StringLiteral      ::=      ('"' (EscapeQuot | [^"])* '"') | ("'" (EscapeApos | [^'])* "'") /* ws: explicit */
[75]      EscapeQuot     ::=      '""'
[76]      EscapeApos     ::=      "''"

我不确定是否已有功能可以使用此功能:

function xpath_quote($str, $quotation='"') {
    if ($quotation != '"' && $quotation != "'") return false;
    return str_replace($quotation, $quotation.$quotation, $str);
}

用法:

'boolean(/html/body//'.$heading.'[contains(.,"'.xpath_quote($keyword).'")])'