PHP XMLReader moveToFirstAttribute()用法及代码示例

XMLReader::moveToFirstAttribute()函数是PHP中的内置函数，用于将光标置于元素的第一个属性上。当我们对一个元素有多个属性并且想要获取第一个属性时，或者当我们要检查一个元素是否具有任何属性时，此函数很有用。

用法:

bool XMLReader::moveToFirstAttribute( void )

参数：此函数不接受任何参数。

返回值：如果成功，此函数将返回TRUE，否则将返回FALSE。

以下示例说明了PHP中的XMLReader::moveToFirstAttribute()函数：

范例1：

• data.xml

  <?xml version="1.0" encoding="utf-8"?> 
  <div> 
      <h1>Foo Bar</h1> 
  </div>
• index.php

  <?php 
    
  // Create a new XMLReader instance 
  $XMLReader = new XMLReader(); 
    
  // Open the XML file 
  $XMLReader->open('data.xml'); 
    
  // Iterate through the XML nodes 
  // to reach the h1 node 
  $XMLReader->read(); 
  $XMLReader->read(); 
  $XMLReader->read(); 
    
  // Checking if attribute is there or not 
  if ($XMLReader->moveToFirstAttribute()) { 
      echo "Attribute is there"; 
  } else { 
      echo "No, attributes."; 
  } 
  ?>
• 输出：

  No, attributes.

程序2:

• data.xml

  <?xml version="1.0" encoding="utf-8"?> 
  <div> 
      <h1 attrib1="value1" 
          attrib2="value2" 
          attrib3="value">  
       Foo Bar  
      </h1> 
  </div>
• index.php

  <?php 
    
  // Create a new XMLReader instance 
  $XMLReader = new XMLReader(); 
    
  // Open the XML file 
  $XMLReader->open('data.xml'); 
    
  // Iterate through the XML nodes 
  // to reach the h1 node 
  $XMLReader->read(); 
  $XMLReader->read(); 
  $XMLReader->read(); 
    
  // Move to attribute with name attrib3 
  $XMLReader->moveToAttribute("attrib3"); 
    
  // Print name of element 
  echo "Before:<br> We are currently "
        . "at:$XMLReader->name<br>"; 
    
  // Move to first attribute 
  $XMLReader->moveToFirstAttribute(); 
    
  // Print name of element 
  echo "After:<br> We are currently "
        . "at:$XMLReader->name"; 
  ?>
• 输出：

  Before:
  We are currently at:attrib3
  After:
  We are currently at:attrib1

参考： https://www.php.net/manual/en/xmlreader.movetofirstattribute.php