php进行压缩 ob_gzhandler函数有3种方法

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/**
     * Valid Email
     *
     * @access  public
     * @param   string
     * @return  bool
     */
    function valid_email($str)
    {
        return ( ! preg_match("/^([a-z0-9+_-]+)(.[a-z0-9+_-]+)*@([a-z0-9-]+.)+[a-z]{2,6}$/ix", $str)) ? FALSE : TRUE;
    }

/**
 * 判断email格式是否正确
 * @param $email
 */
function is_email($email) {
    return strlen($email) > 6 && preg_match("/^[w-.]+@[w-.]+(.w+)+$/", $email);
}

/**
 * Verifies that an email is valid.
 *
 * Does not grok i18n domains. Not RFC compliant.
 *
 * @since 0.71
 *
 * @param string $email Email address to verify.
 * @param boolean $deprecated Deprecated.
 * @return string|bool Either false or the valid email address.
 */
function is_email( $email, $deprecated = false ) {
    if ( ! empty( $deprecated ) )
        _deprecated_argument( __FUNCTION__, '3.0' );
 
    // Test for the minimum length the email can be
    if ( strlen( $email ) < 3 ) {
        return apply_filters( 'is_email', false, $email, 'email_too_short' );
    }
 
    // Test for an @ character after the first position
    if ( strpos( $email, '@', 1 ) === false ) {
        return apply_filters( 'is_email', false, $email, 'email_no_at' );
    }
 
    // Split out the local and domain parts
    list( $local, $domain ) = explode( '@', $email, 2 );
 
    // LOCAL PART
    // Test for invalid characters
    if ( !preg_match( '/^[a-zA-Z0-9!#$%&'*+/=?^_`{|}~.-]+$/', $local ) ) {
        return apply_filters( 'is_email', false, $email, 'local_invalid_chars' );
    }
 
    // DOMAIN PART
    // Test for sequences of periods
    if ( preg_match( '/.{2,}/', $domain ) ) {
        return apply_filters( 'is_email', false, $email, 'domain_period_sequence' );
    }
 
    // Test for leading and trailing periods and whitespace
    if ( trim( $domain, " tnrx0B." ) !== $domain ) {
        return apply_filters( 'is_email', false, $email, 'domain_period_limits' );
    }
 
    // Split the domain into subs
    $subs = explode( '.', $domain );
 
    // Assume the domain will have at least two subs
    if ( 2 > count( $subs ) ) {
        return apply_filters( 'is_email', false, $email, 'domain_no_periods' );
    }
 
    // Loop through each sub
    foreach ( $subs as $sub ) {
        // Test for leading and trailing hyphens and whitespace
        if ( trim( $sub, " tnrx0B-" ) !== $sub ) {
            return apply_filters( 'is_email', false, $email, 'sub_hyphen_limits' );
        }
 
        // Test for invalid characters
        if ( !preg_match('/^[a-z0-9-]+$/i', $sub ) ) {
            return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
        }
    }
 
    // Congratulations your email made it!
    return apply_filters( 'is_email', $email, $email, null );
}

<?php
/**
 * Tanphp framework
 *
 *
 * @category   Tanphp
 * @package    Data_structure
 * @copyright  Copyright (c) 2012 谭博  tanbo.name
 * @version    $Id: Tree.php 25024 2012-11-26 22:22:22 tanbo $
 */

/**
 * 树形结构数据存取类
 *
 * 用于对树形结构数据进行快速的存取
 *
 * @param array $arr 参数必须为标准的二维数组，包含索引字段（id）与表示树形结构的字段(path),如example中所示
 *
 * @example <code>
 * $arr = array(
 *  array( 'id' => 1, 'name' => 'php', 'path' => '1' ),
 *  array( 'id' => 3, 'name' => 'php1', 'path' => '1-3' ),
 *  array( 'id' => 2, 'name' => 'mysql', 'path' => '2' ),
 *  array( 'id' => 6, 'name' => 'mysql1', 'path' => '2-6' ),
 *  array( 'id' => 7, 'name' => 'mysql2', 'path' => '2-7' ),
 *  array( 'id' => 5, 'name' => 'php11', 'path' => '1-3-5' ),
 *  array( 'id' => 4, 'name' => 'php2', 'path' => '1-4' ),
 *   );
 *  $cate = new Tree($arr);
 * 
 *  $data = $cate->getChild(2);
 * 
 *  print_r($data->toArray());
 * </code>
 *
 */

class Tree
{
    public  $_info;                             //节点信息
    public  $_child = array();                  //子节点
    private $_parent;                           //父节点
    private $_data;                             //当前操作的临时数据
    private static $_indexs         = array();  //所有节点的索引
    private static $_index_key      = 'id';     //索引键
    private static $_tree_key       = 'path';   //树形结构表达键
    private static $_tree_delimiter = '-';      //属性结构表达分割符
   
   
   
    /**
     * 构造函数
     *
     * @param array $arr
     * @param boole $force_sort 如果为真，将会强制对$arr 进行排序
     * @return void
     */
    public function __construct(array $arr = array(),  $force_sort=true)
    {
        if ($force_sort === true) {
            $arr=$this->_array_sort($arr, self::$_tree_key);
        }
        if (!empty($arr)) {
            $this->_init($arr);
        }
    }
   
    /**
     * 初始存储树形数据
     *
     * @param array $arr
     * @return void
     */
    private function _init(array $arr)
    {
        foreach ($arr as $item) {
            $path        = $item[self::$_tree_key];
            $paths       = explode(self::$_tree_delimiter, $path);
            $count_paths = count($paths);
            $parent_id   = isset($paths[$count_paths-2]) ? $paths[$count_paths-2] : NULL;
           
            if (   $count_paths>1                                   //如果有父级
                && array_key_exists($parent_id, self::$_indexs)      //父级已经被存入索引
                && self::$_indexs[$parent_id] instanceof Tree    //父级为Tree对象
            ) {
                self::$_indexs[$parent_id]->addChild($item);
            } elseif ($count_paths == 1) {
                $this->addChild($item);
            } else {
                throw new Exception("path数据错误".var_export($item, true));
            }
           
        }
       
        //print_r(self::$_indexs);
    }
   
    /**
     * 添加子节点
     *
     * @param array $item
     * @return void
     */
    public function addChild(array $item, $parent = NULL)
    {
        $child          = new Tree();
        $child->_info   = $item;
        $child->_parent = $parent == NULL ? $this : $parent;
        $child->_parent->_child[] =  $child;
       
        $this->_addIndex($item, $child->_getSelf());
    }
   
    /**
     * 添加节点到索引
     *
     * @param array $item
     * @param mix $value
     * @return void
     */
    private function _addIndex(array $item, $value)
    {
        if (array_key_exists(self::$_index_key, $item) && is_int($item[self::$_index_key])) {
            self::$_indexs[$item[self::$_index_key]] = $value;
        } else {
            throw new Exception("id字段不存在或者不为字符串");
        }
    }
   
   
    /**
     * 获取对自己的引用
     *
     * @return Tree object quote
     */
    private function _getSelf()
    {
        return $this;
    }
   
    /**
     * 获取指定id的节点的子节点
     *
     * @param int $id
     * @return Tree object
     */
    public function getChild($id)
    {
        $data       = self::$_indexs[$id]->_child;
        $this->_data = $data;
        return $this;
    }
   
    /**
     * 获取指定id的节点的父节点
     *
     * @param int $id
     * @return Tree object
     */
    public function getParent($id)
    {
        $data = self::$_indexs[$id]->_parent;
        $this->_data = $data;
        return $this;
    }
   
    /**
     * 获取指定id的节点的同级节点
     *
     * @param int $id
     * @return Tree object
     */
    public function getBrother($id)
    {
        $data = self::$_indexs[$id]->_parent->_child;
        $this->_data = $data;
        return $this;
    }
   
    /**
     * 将Tree对象转化为数组
     *
     * @param  object $object
     * @return array
     */
     public function toArray($obj = NULL)
     {
        $obj  = ($obj === NULL) ? $this->_data : $obj;
        $arr  = array();
        $_arr = is_object($obj) ? $this->_getBaseInfo($obj) : $obj;
       
        if (is_array($_arr)) {
            foreach ($_arr as $key => $val){
               
                $val = (is_array($val) || is_object($val)) ? $this->toArray($val) : $val;
                   
                $arr[$key] = $val;
            }
        } else {
            throw new Exception("_arr不是数组");
        }
       
    
        return $arr;
    }
   
    /**
     * 过滤_parent等字段，以免造成无限循环
     *
     * @param object $obj
     * @return void
     */
    private function _getBaseInfo($obj)
    {
        $vars = get_object_vars($obj);
        $baseInfo['_info']  =  $vars['_info'];
        $baseInfo['_child'] =  $vars['_child'];
        return $baseInfo;
    }
   
    /**
     * 二维数组排序
     *
     * 根据指定的键名对二维数组进行升序或者降序排列
     *
     * @param array  $arr 二维数组
     * @param string $keys
     * @param string $type 必须为 asc或desc
     * @throws 当参数非法时抛出异常
     * @return 返回排序好的数组
     */
    private function _array_sort(array $arr, $keys, $type = 'asc') {
        if (!is_string($keys)) {
            throw new Exception("非法参数keys:参数keys的类型必须为字符串");
        }
   
        $keysvalue = $new_array = array();
        foreach ($arr as $k=>$v) {
            if (!is_array($v) || !isset($v[$keys])) {
                throw new Exception("参数arr不是二维数组或arr子元素中不存在键'{$keys}'");
            }
            $keysvalue[$k] = $v[$keys];
        }
   
        switch ($type) {
            case 'asc':
                asort($keysvalue);
                break;
            case 'desc':
                arsort($keysvalue);
                break;
            default:
                throw new Exception("非法参数type ：参数type的值必须为 'asc' 或 'desc'");
        }
   
        reset($keysvalue);
        foreach ($keysvalue as $k=>$v) {
            $new_array[$k] = $arr[$k];
        }
        return $new_array;
    }
   
}

?>

if (defined('CONST_NAME')) {
    //do something 
}

if (isset($var_name)) {
    //do something
}

函数检测用function_exists，注意待检测的函数名也需要使用引号，如：

if (function_exists('fun_name')) {
 fun_name();
}

<?php
/* 判断常量是否存在*/
if (defined('MYCONSTANT')) {
echo MYCONSTANT;
}
//判断变量是否存在
if (isset($myvar)) {
echo "存在变量$myvar.";
}
//判断函数是否存在
if (function_exists('imap_open')) {
echo "存在函数imag_openn";
} else {
echo "函数imag_open不存在n";
}
?>