PHP basic operators and control structure process code examples

PHP introductory tutorial operator and control structure process, combined with examples, a detailed analysis of PHP's basic assignment, auto-increment, comparison, ternary operator, as well as if statements, switch statements, for statements, etc. Flow control Tips for using statements. The code is as follows:

Demo1.php

<?php
  $username = "chaoyv";
  echo "His name is $username !";
  $username2 = "吴者然";
  echo "His name is $username2 ! ";
  echo "<br/>";
  echo "His name is ".$username2."，阅谁问君诵，\n水落清香浮。";
  echo "<br/>";
  echo "His name is ".$username2."，阅谁问君诵，\t水落清香浮。";
  echo &#39;His name is $username2 ! &#39;;//无法解析 $username2
?>

Demo2.php

<?php
  $a = 5;
  $b = 6;
// $c = $a + $b;
// echo $c;
// $a += $b;//$a=$a+$b;
// echo $a;
// $a=++$b;//$b=$b+1
// echo $a;  //7
// echo $b;  //7
  $a=$b++;
  echo $a;  //6
  echo $b; //7
?>

Demo3.php

<?php
// $a = 5;
// $b = &#39;5&#39;;
// //在网页上（真true）的体现是1，假的体现是空
// //恒等必须数据类型也一样
// //$a === $b 返回的是一个假，false
// echo !($a===$b);  //这个会打印出什么呢？
  $a = 5;
  $b = 5;
  $c = ($a ==$b);
  //echo $c;
  $d = 8;
  $e = 7;
  $f = ($d ==$e);
  //echo $c&&$f;
  echo $c||$f;
?>

Demo4.php

<?php
  $total = 80;
  //三元运算符
  //如果判断为真true,那么整体返回第一个字符串，否则返回第二个字符串
  $sum = $total>50?&#39;成功&#39;:&#39;失败&#39;;
  echo $sum;
?>

Demo5.php

<?php
  //在开发过程中，最好将错误都暴露出来。
  //$a = 100/0; Warning: pision by zero in C:\AppServ\www\Basic3\Demo5.php on line 2
  $a = @(100/0);
  echo $a;
?>

Demo6.php

<?php
  //if 条件判断语句
  $userAge = 25;
  //if 后面的括号是布尔表达式，返回的结果是1或者空
  //{}块语句
// if($userAge>18){
//   echo &#39;成功&#39;;
// }
  //如果。。。否则
// if($userAge>18){
//   echo &#39;成功&#39;;
// }else{
//   echo &#39;失败&#39;;
// }
  //多重线路
  if($userAge<18){
    echo &#39;<18&#39;;
  }elseif ($userAge<30){
    echo &#39;<25&#39;;
  }else{
    echo &#39;通过&#39;;
  }
?>

Demo7.php

<?php
  //多重线路
  //break退出问题，叫做中途退出这个条件判断
  $weekday = 3;
  switch ($weekday){
    case 1:
      echo &#39;今天星期一&#39;;
      break;
    case 2:
      echo &#39;今天星期二&#39;;
      break;
    case 3:
      echo &#39;今天星期三&#39;;
      break;
    case 4:
      echo &#39;今天星期四&#39;;
      break;
    default:
      echo &#39;不清楚&#39;;
  }
?>

Demo8.php

<?php
  //while 循环
  //当判断表达式为假的时候，退出循环
  $a = 10;
  while ($a > 0){
    echo $a;
    $a--;
    echo &#39;<br/>&#39;;
  }
?>

Demo9.php

<?php
  //for
  for($a=10;$a>0;$a--){
    echo $a;
    echo &#39;<br/>&#39;;
  }
?>

Demo10.php

<?php
  //do while
  $a = 10;
  do{
    echo $a;
    echo &#39;<br/>&#39;;
    $a--;
  }while($a>0);
?>

Demo11.php

<?php
// for($i = 0;$i<10;$i++){
//   //在这个循环里面嵌套一个 IF 判断语句
//   if($i==5){
//     break;//中途退出循环
//   }
//   echo $i.&#39;<br/>&#39;;
// }
// for($i = 0;$i<10;$i++){
//   //在这个循环里面嵌套一个 IF 判断语句
//   if($i==5){
//     exit;//退出整个程序
//   }
//   echo $i.&#39;<br/>&#39;;
// }
// echo &#39;我还会执行的&#39;;
  for($i = 0;$i<10;$i++){
    //在这个循环里面嵌套一个 IF 判断语句
    if($i==5){
      continue;//退出当前本次循环，并且继续下次循环 OK
    }
    echo $i.&#39;<br/>&#39;;
  }
?>

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