PHP是一種廣泛使用的服務器端腳本語言，目前被大量的網站使用。PHP本身并沒有提供繪圖功能，但是通過第三方庫可以方便地實現。 其中，JPGraph和pChart是兩個非常著名且廣泛使用的PHP繪圖庫。 JPGraph能夠繪制精美的線性圖、柱狀圖、散點圖等，也能夠按需定制繪圖特性。它的特點是能夠通過簡單易懂的代碼實現繪圖需求，同時支持多種數據源，包括MySQL、SQLServer和CSV等等。舉個例子，下面的代碼實現了一個使用JPGraph繪制柱狀圖的功能：

require_once ('jpgraph/jpgraph.php');
require_once ('jpgraph/jpgraph_bar.php');
$data = array(44,53,31,61,38,50);
$graph = new Graph(550,400);
$graph->SetScale("textlin");
$graph->SetShadow();
$graph->title->Set("Sales per month for 2010");
$graph->subtitle->Set("This is just a test");
$graph->xaxis->title->Set("Month");
$graph->yaxis->title->Set("Sales");
$graph->xaxis->SetTickLabels(array('Jan','Feb','Mar','Apr','May','Jun'));
$barplot = new BarPlot($data);
$barplot->SetColor("white");
$barplot->SetFillColor("#cc1111");
$graph->Add($barplot);
$graph->Stroke();

pChart則是PHP中最優秀的開源圖表工具之一，支持各種各樣的圖表類型，如柱形圖、餅圖、折線圖等等。它的特點是使用方便、代碼簡單，同時支持SVG、Flash動畫等輸出格式。舉個例子，下面的代碼實現了一個使用pChart繪制餅圖的功能：

require_once('pChart2.0.0/class/pData.class.php');
require_once('pChart2.0.0/class/pChart.class.php');
$data = array(20,50,30);
$myData = new pData();
$myData->addPoints($data,'Score');
$myData->setSerieWeight('Score',2);
$myData->setAxisName(0,"Scores");
$myData->addPoints(array("A","B","C"),"Labels");
$myData->setSerieDescription("Labels","Score");
$myData->setAbscissa("Labels");
$myPicture = new pChart(450,250);
$myPicture->Antialias = FALSE;
$myPicture->background->Fill(255,255,255);
$pieChart = new pPie($myPicture,$myData);
$pieChart->setSliceColor(0,array("R"=>255,"G"=>255,"B"=>255));
$pieChart->setSliceColor(1,array("R"=>0,"G"=>100,"B"=>255));
$pieChart->setSliceColor(2,array("R"=>255,"G"=>0,"B"=>0));
$pieChart->draw3DPie(125,125,array("Radius"=>100,"DrawLabels"=>FALSE,"LabelStacked"=>TRUE,"WriteValues"=>TRUE,"DataGapAngle"=>0,"DataGapRadius"=>10,"Border"=>TRUE));
$myPicture->Render();

總之，PHP中的繪圖庫可以很方便地滿足我們繪制各種圖表的需求。在實際應用中，我們可以根據具體需求選擇JPGraph或pChart等開源繪圖庫進行使用。