PHP xmlwriter_start_pi()用法及代码示例

定义和用法

XML 是一种 mark-up 语言，用于在网络上共享数据，XML 用于人类 read-able 和机器 read-able。 XMLWriter 扩展内部具有 libxml xmlWriter API，用于编写/创建 XML 文档的内容。由此生成的 XML 文档是非缓存的和 forward-only。

这个xmlwriter_start_pi()函数接受一个 XMLWriter 类的对象和一个表示处理指令目标的字符串作为参数，并创建一个起始 PI 标记。

用法

xmlwriter_start_pi($writer, $str);

参数

Sr.No	参数及说明
1	writer(Mandatory) 这是 XMLWriter 类的一个对象，表示您要修改/创建的 XML 文档。
2	str(Mandatory) 这是一个字符串值，表示处理指令的目标。

返回值

此函数返回一个布尔值，成功时为 TRUE，失败时为 FALSE。

PHP版本

这个函数最初是在 PHP 版本 5 中引入的，并且适用于所有后续版本。

示例

下面的例子演示了xmlwriter_start_pi()函数 -

<?php
   //Opening a writer
   $uri = "result.xml";
   $writer = xmlwriter_open_uri($uri);

   //Setting the indentation on
   xmlwriter_set_indent($writer, TRUE);

   //Starting the document
   xmlwriter_start_document($writer);
   xmlwriter_set_indent_string($writer, "  ");

   //Starting the processing instruction
   xmlwriter_start_pi($writer, 'php');   
   
   //Write the instruction content of the processing instruction
   xmlwriter_text($writer, 'echo $a;');   
   
   //Ending the processing instruction
   xmlwriter_end_pi($writer); 

   //Setting the indentation
   xmlwriter_set_indent_string($writer, "    ");

   //Starting an element
   xmlwriter_start_element($writer, 'Tutorial');
   xmlwriter_start_element($writer, 'name');
   
   //Adding text to the element
   xmlwriter_text($writer, 'JavaFX');  
   xmlwriter_end_element($writer);
   xmlwriter_start_element($writer, 'Author');
   
   //Adding text to the element
   xmlwriter_text($writer, 'Krishna');  
   xmlwriter_end_element($writer);

   //Ending the element
   xmlwriter_end_element($writer);
   
   //Ending the document
   xmlwriter_end_document($writer);
?>

这将生成以下 XML 文档 -

<?xml version="1.0"?>
<?php echo $a;?>
<Tutorial>
   <name>JavaFX</name>
   <Author>Krishna</Author>
</Tutorial>

示例

以下是面向对象风格的此函数的示例 -

<?php
   //Creating an XMLWriter
   $writer = new XMLWriter();

   //Opening a writer
   $uri = "result.xml";
   $writer->openUri($uri);

   //Setting the indentation on
   $writer->setIndent(TRUE);

   //Starting the document
   $writer->startDocument();
   $writer->setIndentString("  ");

   //Starting the processing instruction
   $writer->startPi('php');   
   
   //Write the instruction content of the processing instruction
   $writer->text('echo $a;');   
   
   //Ending the processing instruction
   $writer->endPi(); 

   //Setting the indentation
   $writer->setIndentString("    ");

   //Starting an element
   $writer->startElement('Tutorial');
   $writer->startElement('name');
   
   //Adding text to the element
   $writer->text('JavaFX');  
   $writer->endElement();
   $writer->startElement('Author');
   
   //Adding text to the element
   $writer->text('Krishna');  
   $writer->endElement();

   //Ending the element
   $writer->endElement();
   
   //Ending the document
   $writer->endDocument();
?>

这将生成以下 XML 文档 -

<?xml version="1.0"?>
<?php echo $a;?>
<Tutorial>
   <name>JavaFX</name>
   <Author>Krishna</Author>
</Tutorial>