A QueryPath Tutorial(一个简易说明)
QueryPath makes use of method chaining to provide a concise suite of tools for manipulating a DOM.
The basic principle of method chaining is that each method returns an object upon which additional methods can be called. In our case, the QueryPath object usually returns itself.
Let's take a look at an example to illustrate:
$qp = qp(QueryPath::HTML_STUB); // Generate a new QueryPath object.(创建一个 QP 对象)
$qp2 = $qp->find('body'); // Find the body tag.(找到 "body" 标签)
// Now the surprising part:(请看下面让你惊奇的地方)
if ($qp === $qp2) {
// This will always get printed.(它总是会这样输出)
print "MATCH";
}
Why does $qp always equal $qp2? Because the find() function does all of its data gathering and then returns the QueryPath object.
This might seem esoteric, but it all has a very practical rationale. With this sort of interface, we can chain lots of methods together:
(你可以向使用 jQuery 一样来连缀方法)
qp(QueryPath::HTML_STUB)->find('body')->text('Hello World')->writeHTML();
In this example, we have four method calls:
qp(QueryPath::HTML_STUB): Create a new QueryPath object and provide it with a stub of an HTML document. This returns the QueryPath object.
find('body'): This searches the QueryPath document looking for an element named 'body'. That element is, of course, the <body></body> portion of the HTML document. When it finds the body element, it keeps an internal pointer to that element, and it returns the QueryPath object (which is now wrapping the body element).
text('Hello World'): This function takes the current element(s) wrapped by QueryPath and adds the text Hello World. As you have probably guessed, it, too, returns a QueryPath object. The object will still be pointing to the body element.
writeHTML(): The writeHTML() function prints out the entire document. This is used to send the HTML back to the client. You'll never guess what this function returns. Okay, you guessed it. QueryPath.
So at the end of the chain above, we would have created a document that looks something like this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"></meta> <title>Untitled</title> </head> <body>Hello World</body> </html>
Most of that HTML comes from the QueryPath::HTML_STUB. All we did was add the Hello World text inside of the <body></body> tags.
Not all QueryPath functions return QueryPath objects. Some tools need to return other data. But those functions are well-documented in the included documentation.
These are the basic principles behind QueryPath. Now let's take a look at a larger example that exercises more of the QueryPath API.
A Longer Example
This example illustrates various core features of QueryPath.
In this example, we use some of the standard QueryPath functions (most of them implementing the jQuery interface) to build a new web page from scratch.
Each line of the code has been commented individually. The output from this is shown in a separate block beneath.
<?php
/**
* Using QueryPath.
*
* This file contains an example of how QueryPath can be used
* to generate web pages.
* @package QueryPath
* @subpackage Examples
* @author M Butcher <matt@aleph-null.tv>
* @license LGPL The GNU Lesser GPL (LGPL) or an MIT-like license.
*/
// Require the QueryPath core.
require_once 'QueryPath/QueryPath.php';
// Begin with an HTML stub document (XHTML, actually), and navigate to the title.
qp(QueryPath::HTML_STUB, 'title')
// Add some text to the title
->text('Example of QueryPath.')
// Now look for the <body> element
->find(':root body')
// Inside the body, add a title and paragraph.
->append('<h1>This is a test page</h1><p>Test text</p>')
// Now we select the paragraph we just created inside the body
->children('p')
// Add a 'class="some-class"' attribute to the paragraph
->attr('class', 'some-class')
// And add a style attribute, too, setting the background color.
->css('background-color', '#eee')
// Now go back to the paragraph again
->parent()
// Before the paragraph and the title, add an empty table.
->prepend('<table id="my-table"></table>')
// Now let's go to the table...
->find('#my-table')
// Add a couple of empty rows
->append('<tr></tr><tr></tr>')
// select the rows (both at once)
->children()
// Add a CSS class to both rows
->addClass('table-row')
// Now just get the first row (at position 0)
->eq(0)
// Add a table header in the first row
->append('<th>This is the header</th>')
// Now go to the next row
->next()
// Add some data to this row
->append('<td>This is the data</td>')
// Write it all out as HTML
->writeHTML();
?> The code above produces the following HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"></meta> <title>Example of QueryPath.</title> </head> <body> <table id="my-table"> <tr class="table-row"><th>This is the header</th></tr> <tr class="table-row"><td>This is the data</td></tr> </table> <h1>This is a test page</h1> <p class="some-class" style="background-color: #eee">Test text</p></body> </html>
Now you should have an idea of how QueryPath works. Grab a copy of the library and try it out! Along with the source code, you will get a nice bundle of HTML files that cover every single public function in the QueryPath library (no kidding). There are more examples there, too.
不错的东东！赶紧 Grab 它吧~~！
QueryPath PHP 中的jQuery
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