Detailed explanation of operators and control structure processes in PHP introductory tutorial

This article describes the operator and control structure process of PHP introductory tutorial with examples. Share it with everyone for your reference, the details are 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: Division 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;;
  }
?>

I hope this article will be helpful to everyone in PHP programming.

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