Detailed explanation of the usage examples of PHP flow control statements

if (including if..elseif..else extended examples) Conditional statement, execute the corresponding statement according to the given conditions, is a basic statement

<?php　　
//应用if..elseif..else语句实现企业客服管理系统的用户登录功能 
$username=&#39;yiciyun&#39;;
$password=&#39;123456&#39;;
if (!empty($_POST[&#39;user&#39;])&&!empty($_POST[&#39;pwd&#39;])){    //判断用户名和密码是否为空
    $user=$_POST[&#39;user&#39;];
    $pwd=$_POST[&#39;pwd&#39;];
    if ($user!=$username){                            //判断用户名是否相等
        echo &#39;用户名错误&#39;;
    }
    elseif ($pwd!=$password){                        //判断密码是否相等
        echo &#39;密码错误&#39;;
    }
    else {                                            //如果都相等,输出登录成功
        echo &#39;登录成功&#39;;            
    }
}
else{
    echo &#39;用户名或密码不能为空&#39;;
}
?>

while Loop statement, loop specified according to the satisfied condition statement until the condition is not met

do..while loop statement is basically the same as the while loop statement. The difference is that the do..while statement first executes the specified statement once and then makes a judgment

for Loop statement, loops according to the given conditions until the conditions are not met, providing a more complex loop mechanism

<?php    
//九九乘法表
for($i=1;$i<10;$i++){
    for ($j=1;$j<=$i;$j++){
        echo "$i*$j=".$i*$j;
        echo "\t";
    }
    echo "<br>";
}
?>

foreach Loop statement, good at processing arrays, extracting each unit keys and values ​​until the end of the array

<?php　　
//应用foreach语句循环输出数组内的键和值
$book=array("7人"=>"ASP 部门","5人"=>"VB 部门","6人"=>"PHP 部门","8人"=>"Java 部门");
foreach($book as $value){
    echo "$value<br/>";
}
foreach($book as $key=>$value){
    echo "$key=>$value<br/>";
}
?>

switch Conditional statements, switch statements are executed line by line. No code is executed at the beginning. Only when the value in a case statement and switch expression When the value of matches, PHP will start executing the statement until the switch program section ends or the first break statement is encountered. If break is not written at the end of the case statement section, PHP will continue to execute the next case. Statement segment.

<?php    
//应用switch语句分别对用户名和密码进行判断
$username = &#39;mr&#39;;
$password = &#39;mrsoft&#39;;
switch($_POST[&#39;user&#39;]){
    case $username : $u = true; break;
    case &#39;&#39;: echo "用户名不能为空 <br />"; break;
    default : echo "用户名错误 <br />"; break;
}
switch($_POST[&#39;pwd&#39;]){
    case $password : $p = true; break;
    case &#39;&#39; : echo "密码不能为空 <br />"; break;
    default : echo "密码错误 <br />"; break;
}
if(isset($u,$p)){
    echo "登录成功";
}
?>

<?php    
//应用switch语句判断今天是星期几
$week=date("w");
switch ($week){
    case 0:echo "星期日<br/>";break;
    case 1:echo "星期一<br/>";break;
    case 2:echo "星期二<br/>";break;
    case 3:echo "星期三<br/>";break;
    case 4:echo "星期四<br/>";break;
    case 5:echo "星期五<br/>";break;
    case 6:echo "星期六<br/>";break;
}
?>

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