Dom class is miss

centos5.2上的php5默认是没有安装DOM Functions的，

使用测试用例如下：

>vi dom.php

<?php

$doc = new DOMDocument();

$doc->load('books.xml');

$books = $doc->getElementsByTagName("book");

foreach($books as $book)
{
$authors = $book->getElementsByTagName("author");
$author = $authors->item(0)->nodeValue;

$publishers = $book->getElementsByTagName("publisher");
$publisher = $publishers->item(0)->nodeValue;

$titles = $book->getElementsByTagName("title");
$title = $titles->item(0)->nodeValue;

echo "$title-$author-$publisher\n";
}

>vi books.xml

<books>
  <book>
  <author>Jack Herrington</author>
  <title>PHP Hacks</title>
  <publisher>O'Reilly</publisher>
  </book>
  <book>
  <author>Jack Herrington</author>
  <title>Podcasting Hacks</title>
  <publisher>O'Reilly</publisher>
  </book>
</books>

>php dom.php

此时显示PHP Fatal error:  Class 'DOMDocument' not found in /home/dom.php on line 3

那意味着php-dom没有被安装

可以通过yum可以安装；

>yum install php-dom

=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
php-xml                 i386       5.1.6-23.el5     base               95 k
Updating:
php-common              i386       5.1.6-23.el5     base              154 k
Updating for dependencies:
php                     i386       5.1.6-23.el5     base              1.2 M
php-cli                 i386       5.1.6-23.el5     base              2.1 M
php-ldap                i386       5.1.6-23.el5     base               35 k

Transaction Summary
=============================================================================
Install      1 Package(s)        
Update       4 Package(s)        
Remove       0 Package(s)        

Total download size: 3.5 M
Is this ok [y/N]: y
Downloading Packages:
(1/5): php-common-5.1.6-2 100% |=========================| 154 kB    00:00    
(2/5): php-5.1.6-23.el5.i 100% |=========================| 1.2 MB    00:05    
(3/5): php-xml-5.1.6-23.e 100% |=========================|  95 kB    00:00    
(4/5): php-ldap-5.1.6-23. 100% |=========================|  35 kB    00:00    
(5/5): php-cli-5.1.6-23.e 100% |=========================| 2.1 MB    00:09

OK，安装完成后再看看php的运行情况

>php dom.php
PHP Hacks-Jack Herrington-O'Reilly
Podcasting Hacks-Jack Herrington-O'Reilly

同样，对于gd库也可以这样安装

>yum install php-gd