$array = array(1 => 30, 2 => 20, 3 => 20, 4 => 15, 5=> 10 , 6 => 5);
$rand = mt_rand();
$rand = $rand % 101;
$max = 0;
$v = 0;
foreach($array as $key => $value)
{
    $max += $value;
    if($rand <= $max)
    {
        $v = $key;
        break;
    }
}
echo $v;

<?php
$a = array('x' => 50, 'y' => 60);
$b = array('x' => 80, 'y' => 60);
$c = array('x' => 80, 'y' => 70);
echo rad2deg(atan2($c['y'] - $a['y'], $c['x'] - $a['x']));
?>

/**
Example: 
 
$page = (isset($this->params['named']['page'])) ? $this->params['named']['page'] : 1;
// 导入分页类
App::import('Vendor', 'page_class');
// 获取公告总数
$total = $this->Bulletin->getBulletinTotal();
$perpage = ITEMPREPAGE;
$offset = $perpage * ($page - 1);
$pagebar = new Pagebar($total, $page, $offset, $perpage);
$pagenav = $pagebar->construct_page_nav($total, $page, SYSTEMURL . '/bulletins/index', null, null);
*/
 
<?php
class Pagebar
{
 
    var $perpage = 20;
	/**
	* Ensures that the variables for a multi-page display are sane
	*
	* @param	integer	Total number of items to be displayed
	* @param	integer	(ref) Current page number
	* @param	integer	(ref) Desired number of results to show per-page
	*/
	function Pagebar($numresults, &$page, &$limitlower, $perpage)
	{
		$this->perpage = $perpage;
 
		$numpages = ceil($numresults / $this->perpage);
		if ($numpages == 0)
		{
			$numpages = 1;
		}
 
		if ($page < 1)
		{
			$page = 1;
		}
		else if ($page > $numpages)
		{
			$page = $numpages;
		}
 
		$limitlower = ($page - 1) * $this->perpage;
		$limitupper = ($page) * $this->perpage;
 
		if ($limitupper > $numresults)
		{
			$limitupper = $numresults;
			if ($limitlower > $numresults)
			{
				$limitlower = ($numresults - $this->perpage) - 1;
			}
		}
		if ($limitlower < 0)
		{
			$limitlower = 0;
		}
	}
 
	/**
	* Returns the HTML for multi-page navigation
	*
	* @param	integer	Total number of items found
	* @param	integer	Page number being displayed
	* @param	string	Base address for links eg: q.php?t=99{&page=4}
	* @param	string	Ending portion of address for links
	*
	* @return	string	Page navigation HTML
	*/
	function construct_page_nav($results, $pagenumber, $address, $address2 = '', $option = array())
	{
		$perpage = $this->perpage;
 
		$show = array();
		$curpage = 0;
		$pagenav = '';
		$firstlink = '';
		$prevlink = '';
		$lastlink = '';
		$nextlink = '';
 
		if ($results <= $perpage)
		{
			$show['pagenav'] = false;
			return '';
		}
 
		$show['pagenav'] = true;
 
		$total = number_format($results);
		$totalpages = ceil($results / $perpage);
 
		$show['prev'] = false;
		$show['next'] = false;
		$show['first'] = false;
		$show['last'] = false;
 
		if ($pagenumber > 1)
		{
			$prevpage = $pagenumber - 1;
			$prevnumbers = $this->fetch_start_end_total_array($prevpage, $perpage, $results);
			$show['prev'] = true;
		}
		if ($pagenumber < $totalpages)
		{
			$nextpage = $pagenumber + 1;
			$nextnumbers = $this->fetch_start_end_total_array($nextpage, $perpage, $results);
			$show['next'] = true;
		}
 
		// create array of possible relative links that we might have (eg. +10, +20, +50, etc.)
		$pagenavsarr = array(10, 50, 100, 500, 1000);
 
		$pagenavpages = 5;
 
		while ($curpage++ < $totalpages)
		{
			if (abs($curpage - $pagenumber) >= $pagenavpages AND $pagenavpages != 0)
			{
				if ($curpage == 1)
				{
					$firstnumbers = $this->fetch_start_end_total_array(1, $perpage, $results);
					$show['first'] = true;
				}
				if ($curpage == $totalpages)
				{
					$lastnumbers = $this->fetch_start_end_total_array($totalpages, $perpage, $results);
					$show['last'] = true;
				}
				// generate relative links (eg. +10,etc).
				if (in_array(abs($curpage - $pagenumber), $pagenavsarr) AND $curpage != 1 AND $curpage != $totalpages)
				{
					$pagenumbers = $this->fetch_start_end_total_array($curpage, $perpage, $results);
					$relpage = $curpage - $pagenumber;
 
					if ($relpage > 0)
					{
						$relpage = '+' . $relpage;
					}
 
					$pagenav .= "<a onclick=\"$option[onclick]\" class=\"smallfont\" href=\"$address". "/page:$curpage". ($address2 ? '?'.$address2 : '') . "\" title=\"显示结果从 $pagenumbers[first] 到 $pagenumbers[last] 共计 $total 条\"><!--$relpage--> $curpage </a>";
				}
			}
			else
			{
				if ($curpage == $pagenumber)
				{
					$numbers = $this->fetch_start_end_total_array($curpage, $perpage, $results);
					$pagenav .= "	<span class=\"smallfont\" title=\"显示结果从 $numbers[first] 到 $numbers[last] 共计 $total 条\"><strong> $curpage </strong></span>";
				}
				else
				{
					$pagenumbers = $this->fetch_start_end_total_array($curpage, $perpage, $results);
					$pagenav .= "<a onclick=\"$option[onclick]\" class=\"smallfont\" href=\"$address". "/page:$curpage". (($address2) ? '?'.$address2 : '') . "\" title=\"显示结果从 $pagenumbers[first] 到 $pagenumbers[last] 共计 $total 条\"> $curpage </a>";
				}
			}
		}
        $pagenav = "
                <span class=\"disabled\">
                ".(($show['prev']) ? ("<a onclick=\"$option[onclick]\" class=\"smallfont\" href=\"$address".("/page:$prevpage".($address2 ? '?'.$address2 : ''))."\" title=\"上一页 - 结果从 $prevnumbers[first] 到 $prevnumbers[last] 共计 $total\">上一页</a></span>") : ("上一页</span>"))."
 
                $pagenav
 
                ".(($show['next']) ? ("<span><a onclick=\"$option[onclick]\" class=\"smallfont\" href=\"$address/page:$nextpage".($address2 ? '?'.$address2 : '')."\" title=\"下一页 - 结果从 $nextnumbers[first] 到 $nextnumbers[last] 共计 $total\">下一页</a></span>") : ("<span>下一页</span>"))."
 
				<span>第 $pagenumber / $totalpages 页,共 <strong>$total</strong>条记录</span>";
		return $pagenav;
	}
	/**
	* Returns an array so you can print 'Showing results $arr[first] to $arr[last] of $totalresults'
	*
	* @param	integer	Current page number
	* @param	integer	Results to show per-page
	* @param	integer	Total results found
	*
	* @return	array	In the format of - array('first' => x, 'last' => y)
	*/
	function fetch_start_end_total_array($pagenumber, $perpage, $total)
	{
		$first = $perpage * ($pagenumber - 1);
		$last = $first + $perpage;
 
		if ($last > $total)
		{
			$last = $total;
		}
		$first++;
 
		return array('first' => number_format($first), 'last' => number_format($last));
	}
}
?>

ini_set("error_log", "E:\php_error.log");  
error_log($output,0);

<?php
$im = imagecreate(255, 255);
$bg = imagecolorallocate($im, 0, 0, 0);
for($i=255; $i>=0; $i--)
{
    $color = imagecolorallocate($im, $i, $i, $i);
    imagefilledrectangle($im, 0, $i, 255, 1, $color);
}
header("Content-type: image/png");
imagepng($im);
imagedestroy($im);
?>