php流程控制

2024-05-04 23:07:15

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if语句,switch语句,while循环,do…while循环,for循环,foreach循环,break中断循环,continue指令.下面通过星期函数来演示这些.

程序三种流程控制结构

1、顺序结构

2、选择结构

3、循环结构

结果如下实例代码如下:

$d=date("D");

if ($d=="Tue")

echo "今天是星期二";

else

echo "今天不是星期二";

?>

通过数组可以判断星期几.

执行结果应如下实例代码如下:

$srttime=date("w",time());

$array=array('天','一','二','三','四','五','六');

$todaytime=date("Y年m月d日星期{$array[$srttime]}",time());

echo $todaytime;

?>

1. if (条件一) {

 ?⑹?/p>

 }

<HTML>

<HEAD>

<TITLE> IF - 1 </TITLE>

</HEAD>

<BODY>

<?

 $a = 100 ;

 if ( $a == 100 ) {

 echo "A is 100. ";

 }

?>

</BODY>

</HTML>

 或

 if (条件一) {

 ?⑹鲆?/p>

 } else {

 ?⑹龆?/p>

 }

<HTML>

<HEAD>

<TITLE> IF … ELSE - 1 </TITLE>

</HEAD>

<BODY>

 <?

 $a = 120 ;

 if ($a < 100 ) {

 echo " A was small than 100. ";

 }

 else {

 echo " A was big than 100. ";

 }

?>

</BODY>

</HTML>

　

<HTML>

<HEAD>

<TITLE> IF … ELSE - 2 </TITLE>

</HEAD>

<BODY>

 <?

 $file = "files.txt" ;

 if ( file_exists($file) ) { //?z查?n案是否存在

 echo " ?是?n案 files.txt的?热? ";

 readfile ($file) ; //?出?n案?热?br /> }

 else {

 echo " ?o此?n案 ";

 }

 ?>

</BODY>

</HTML>

 或

 if (条件一) {

 ?⑹鲆?/p>

 } elseif {

 ?⑹龆?/p>

 } elseif {

 ?⑹鋈?/p>

 }

 ...........

 else {

 ?⑹?

 }

 <HTML>

 <HEAD>

 <TITLE> IF … ELSEIF … ELSE - 1 </TITLE>

 </HEAD>

 <BODY>

 <?

 $a = 100 ;

 $b = 200 ;

 if ($a > $b) {

 echo "a is bigger than b";

 } elseif ($a == $b) {

 echo "a is equal to b";

 } else {

 print "a is smaller than b";

 }

 ?>

</BODY>

</HTML>

2. while (条件一) { //条件?檎? ??

 ?⑹鲆?/p>

 }

<HTML>

<HEAD>

<TITLE> WHILE </TITLE>

</HEAD>

<BODY>

 <?

 $a = 1 ;

 while ( $a < 10 ) {

 echo "$a ";

 $a++;

 }

 ?>

</BODY>

</HTML>

　

3. do {

 ?⑹?/p>

 } while (条件); //条件?檎? ??

<HTML>

<HEAD>

<TITLE> Do .. WHILE - 1 </TITLE>

</HEAD>

<BODY>

 <?

 $a = 1 ;

 do {

 echo "$a ";

 $a++;

 } while ( $a < 10 )

 ?>

</BODY>

</HTML>

　

4. for (初始条件; 判?嗵跫? 条件改??⑹? {

 ?⑹?/p>

 }

<HTML>

<HEAD>

<TITLE> For - 1 </TITLE>

</HEAD>

<BODY>

 <?

 for ( $a = 1 ; $a < 10 ; $a++ )

 {

 echo "$a ";

 }

 ?>

</BODY>

</HTML>



5. break //中?嗾?诘霓?圈

<HTML>

<HEAD>

<TITLE> BREAK </TITLE>

</HEAD>

<BODY>

 <?

 $abc[0] = '0' ;

 $abc[1] = '1' ;

 $abc[2] = '2' ;

 $a = 0 ;

 while ( $a < 4 )

 {

 if ( $abc[$a] == '2' ) { //若?檎? 跳?while()?圈

 break;

 }

 echo "$a";

 $a++;

 }

 ?>

</BODY>

</HTML>

6. continue //中?嗾?诘霓?圈, 跳到?圈????下一次

<HTML>

<HEAD>

<TITLE> CONTINUE </TITLE>

</HEAD>

<BODY>

 <?

 for ($i=10 ; $i>1 ; $i--) {

 if ($i == 2 ) { //若?檎? ?束?次的for()?圈, ??下一次for()?圈

 continue;

 }

 echo "$i ";

 }

 ?>

</BODY>

</HTML>

7. switch (条件) {

 case 'case值1':

 ?⑹鲆?nbsp; //条件?case值相同,就?部分的?⑹? 直到遇到break才停止

 break;

 case 'case值2:

 ?⑹龆?br /> break;

 ............

 default:

 ?⑹?

 break;

 }

<HTML>

<HEAD>

<TITLE> SWITCH </TITLE>

</HEAD>

<BODY>

 <?

 switch ($i) {

 case 0:

 echo "i equals 0";

 case 1:

 echo "i equals 1";

 case 2:

 echo "i equals 2";

 }

 ?>

</BODY>

</HTML>

　

<HTML>

<HEAD>

<TITLE> Switch - SWITCH </TITLE>

</HEAD>

<BODY>

 <?

 switch ( $a ) {

 case '1':

 echo "one";

 break;

 case '2':

 echo "two";

 break;

 case '3':

 echo "three";

 break;

 case '4':

 echo "four";

 break;

 case '5':

 echo "five";

 break;

 default:

 echo "ZERO";

 break;

 }

?>

</BODY>

</HTML>