讲述PHP递归算法_PHP教程

php还是比较常用的，于是我研究了一下php递归算法，在这里拿出来和大家分享一下，希望对大家有用。php，一个嵌套的缩写名称，是英文超级文本预处理语言（php:hypertext preprocessor）的缩写。php 是一种 html 内嵌式的语言，是一种在服务器端执行的嵌入html文档的脚本语言，语言的风格有类似于c语言，现在被很多的网站编程人员广泛的运用。php 独特的语法混合了 c、java、perl 以及 php 自创新的语法。

PHP具有非常强大的功能，所有的CGI或者JavaScript的功能PHP都能实现，而且支持几乎所有流行的数据库以及操作系统。我们这里详细的介绍一下PHP递归算法。

PHP递归算法代码：

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<OL class=dp-xml><LI class=alt><SPAN><SPAN class=tag><?</SPAN><SPAN class=tag-name>php</SPAN><SPAN> </SPAN></SPAN><LI class=""><SPAN>//定义PI一分的角度的值  </SPAN><LI class=alt><SPAN>define("PII",M_PI/180);  </SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>//新建图像资源，并定义其背景为白色，前景色为黑色  </SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>im</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>imagecreate</SPAN><SPAN>(670,500);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>white</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>imagecolorallocate</SPAN><SPAN>($im,0xFF,0xFF,0xFF);  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>g</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>imagecolorallocate</SPAN><SPAN>($im,0x00,0x00,0x00);  </SPAN></SPAN><LI class=alt><SPAN> </SPAN><LI class=""><SPAN>//从下面实例化的代码可以得知，初始值$x,$y,$L,$a别分为300,500,100,270  </SPAN><LI class=alt><SPAN>functiondrawLeaf($g,$x,$y,$L,$a){  </SPAN><LI class=""><SPAN>global$im;  </SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>B</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>50</SPAN><SPAN>;  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>C</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>9</SPAN><SPAN>;  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>s1</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>2</SPAN><SPAN>;  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>s2</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>3</SPAN><SPAN>;  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>s3</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>1</SPAN><SPAN>.2;  </SPAN></SPAN><LI class=""><SPAN>if($L</SPAN><SPAN class=tag>></SPAN><SPAN>$s1){  </SPAN></SPAN><LI class=alt><SPAN>//计算叶子的定位上面  </SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x2</SPAN><SPAN>=$x+$L*cos($a*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y2</SPAN><SPAN>=$y+$L*sin($a*PII);  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x2R</SPAN><SPAN>=$x2+$L/$s2*cos(($a+$B)*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y2R</SPAN><SPAN>=$y2+$L/$s2*sin(($a+$B)*PII);  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x2L</SPAN><SPAN>=$x2+$L/$s2*cos(($a-$B)*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y2L</SPAN><SPAN>=$y2+$L/$s2*sin(($a-$B)*PII);  </SPAN></SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>//计算叶子的定位下面  </SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x1</SPAN><SPAN>=$x+$L/$s2*cos($a*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y1</SPAN><SPAN>=$y+$L/$s2*sin($a*PII);  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x1L</SPAN><SPAN>=$x1+$L/$s2*cos(($a-$B)*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y1L</SPAN><SPAN>=$y1+$L/$s2*sin(($a-$B)*PII);  </SPAN></SPAN><LI class=""><SPAN>$</SPAN><SPAN class=attribute>x1R</SPAN><SPAN>=$x1+$L/$s2*cos(($a+$B)*PII);  </SPAN></SPAN><LI class=alt><SPAN>$</SPAN><SPAN class=attribute>y1R</SPAN><SPAN>=$y1+$L/$s2*sin(($a+$B)*PII);  </SPAN></SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>//别分画叶子的主干以及叶面  </SPAN><LI class=""><SPAN>ImageLine($im,(int)$x,(int)$y,(int)$x2,(int)$y2,$g);  </SPAN><LI class=alt><SPAN>ImageLine($im,(int)$x2,(int)$y2,(int)$x2R,(int)$y2R,$g);  </SPAN><LI class=""><SPAN>ImageLine($im,(int)$x2,(int)$y2,(int)$x2L,(int)$y2L,$g);  </SPAN><LI class=alt><SPAN>ImageLine($im,(int)$x1,(int)$y1,(int)$x1L,(int)$y1L,$g);  </SPAN><LI class=""><SPAN>ImageLine($im,(int)$x1,(int)$y1,(int)$x1R,(int)$y1R,$g);  </SPAN><LI class=alt><SPAN> </SPAN><LI class=""><SPAN>//再次递归调用本身  </SPAN><LI class=alt><SPAN>drawLeaf($g,$x2,$y2,$L/$s3,$a+$C);  </SPAN><LI class=""><SPAN>drawLeaf($g,$x2R,$y2R,$L/$s2,$a+$B);  </SPAN><LI class=alt><SPAN>drawLeaf($g,$x2L,$y2L,$L/$s2,$a-$B);  </SPAN><LI class=""><SPAN>drawLeaf($g,$x1L,$y1L,$L/$s2,$a-$B);  </SPAN><LI class=alt><SPAN>drawLeaf($g,$x1R,$y1R,$L/$s2,$a+$B);  </SPAN><LI class=""><SPAN>}  </SPAN><LI class=alt><SPAN>}  </SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>//实例化  </SPAN><LI class=""><SPAN>drawLeaf($g,300,500,100,270);  </SPAN><LI class=alt><SPAN>header("Content-type:image/png");  </SPAN><LI class=""><SPAN>imagepng($im);  </SPAN><LI class=alt><SPAN></SPAN><SPAN class=tag>?></SPAN><SPAN>在我个人的PHP编程经验中，递归调用常常与静态变量使用。静态变量的含义可以参考PHP手册。希望下面的代码，会更有利于对递归以及静态变量的理解  </SPAN></SPAN><LI class=""><SPAN> </SPAN><LI class=alt><SPAN>header("Content-type:text/plain");  </SPAN><LI class=""><SPAN>functionstatic_function(){  </SPAN><LI class=alt><SPAN>static$</SPAN><SPAN class=attribute>i</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>0</SPAN><SPAN>;  </SPAN></SPAN><LI class=""><SPAN>if($i++</SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>10</SPAN><SPAN>){  </SPAN></SPAN><LI class=alt><SPAN>echo$i."n";  </SPAN><LI class=""><SPAN>static_function();  </SPAN><LI class=alt><SPAN>}  </SPAN><LI class=""><SPAN>}  </SPAN><LI class=alt><SPAN>static_function(); </SPAN></LI></OL>

这段代码会如数输出1到10的数字。在static_function函数第二次运行时，变量i由于是静态变量，所以仍被保留不被释放，进而可以得到自增的值。

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