源代码:
<HTML> <HEAD></HEAD> <FONT FACE="'Courier New',Verdana, Arial, Helvetica" SIZE=2> <!DOCTYPE html> <html> <body> <FONT COLOR=#ff0000><?php echo(sqrt(0) . " "); echo(sqrt(1) . " "); echo(sqrt(9) . " "); echo(sqrt(0.64) . " "); echo(sqrt(-9)); ?></FONT> </body> </html> </HTML>
运行结果：
<HTML> <HEAD></HEAD> <FONT FACE="'Courier New',Verdana, Arial, Helvetica" SIZE=2> <!DOCTYPE html> <html> <body> <FONT COLOR=#ff0000>0 1 3 0.8 NAN</FONT> </body> </html> </HTML>