Basic syntax structure of PHP conditional statements_PHP tutorial

The conditional statements in PHP are if else, switch and ternary operator. Let me introduce to you some syntax of these conditional statements.

Basic syntax structure of if single branch

if(conditional expression){

//Execute statement;

}

if double branch

Basic grammatical structure

if(conditional expression){

//Execute statement;

}else{

//Execute statement;

}

if multiple branches

The basic grammatical structure is

if(conditional expression){

//Execute statement;

}else if (conditional expression){

//Execute statement;

}else if(conditional expression){

//Execute statement;

}else{//There may be more else if
//Execute statement;
}

☞ Please note the above structure:

1) else if can have one or multiple

2) else can be omitted

Example

The code is as follows

Copy code

代码如下	复制代码
帐号: 密码: if($account == "lord" && $password == "pass"){     echo "欢迎 $_POST[account], 你的密码是 $_POST[password]"; }elseif($_POST[account] == "god" && $_POST[password] == "dog"){     $y = date("Y") - 1911;     $m = date("m");     $d = date("d");     echo "欢迎 $_POST[account], 今天是民国".$y."年".$m."月".$d."日"; }else{     echo "登入失败: 输入的资料: 帐号: $_POST[account] 密码: $_POST[password]"; } ?>

Account:
Password:

if($account == "lord" && $password == "pass"){

echo "Welcome $_POST[account], your password is $_POST[password]";
}elseif($_POST[account] == ​​"god" && $_POST[password] == "dog"){
$y = date("Y") - 1911;
$m = date("m");
$d = date("d");

echo "Welcome $_POST[account], today is the Republic of China".$y."Year".$m."Month".$d."Day";

}else{

echo "Login failed:

---

Input information:
Account: $_POST[account]
Password: $_POST[password]";

}
?>

switch branch statement

Basic grammatical structure

switch(expression){

case constant 1:

代码如下	复制代码
else {     echo "i is not equal to 0, 1 or 2"; } ?>

//Execute statement; break; case constant 2: //Execute statement; break; defual: //Execute statement; break; } Example The following two examples use different methods to achieve the same thing. The first uses if...elseif...else statements, and the other uses switch statements.

The code is as follows	Copy code
else { echo "i is not equal to 0, 1 or 2"; } ?>

The meaning of the above PHP code is: if the variable $i is equal to 0, then output "i equals 0"; if the variable $i is equal to 1, then output "i equals 1"; if the variable $i is equal to 2, then Output "i equals 2"; if neither, output "i is not equal to 0, 1 or 2".

Comparison of switch statement and elseif statement
In a switch statement, the condition is evaluated once and then compared to each case, whereas in an elseif statement, the condition is evaluated again. If your conditions are more complex, or there are multiple loops, it will be faster to use the switch statement.

The code is as follows

代码如下	复制代码
isEmpty=""; $isEmpty=" 非空 "; $test = empty($isEmpty)?"":trim($isEmpty);

Copy code

isEmpty="";

代码如下	复制代码
if (empty($isEmpty)) //条件成立 {     $cookie = ""; } else {     $cookie = trim($isEmpty);   }

$isEmpty=" not empty ";

$test = empty($isEmpty)?"":trim($isEmpty);

Ternary operator?: According to the previous condition empty($isEmpty)true or false, when the condition is true, calculate the expression after ?, and when false, calculate the expression after:.

If you are not used to it, you can change it to the following code

The code is as follows	Copy code
if (empty($isEmpty)) //Condition is true { $cookie = ""; } else { $cookie = trim($isEmpty); }

☞ Please note: 1) There are one to many case statements 2) The defaul statement does not need to be included (according to the business logic of your own code) 3) Usually, after the case statement, break is required to indicate exiting the switch statement 4) Type of constant (int, float, string, Boolean) Supplement Comparison operators. $a == $b equals TRUE if $a equals $b.          $a != $b    Not equal TRUE if $a is not equal to $b. $a $b does not equal TRUE if $a is not equal to $b.           $a $a > $b is greater than TRUE if $a is strictly $b.           $a $ A & GT; = $ B greater than or equal to True, if $ a is greater than or equal to $ b.           Logical operators. $ A and $ B and (logic and) true, if $ a and $ B are True. $ A or $ b or (logic or) true, if $ a or $ b is True.                         $a xor                                                                                                                                     ! $a   Not (logical NOT)   TRUE if $a is not TRUE. $ A && $ b and (logic and) true, if $ a and $ B are True.             $a ||   $b     Or (logical OR)   TRUE if either $a or $b is TRUE.

http://www.bkjia.com/PHPjc/632630.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/632630.htmlTechArticleThe conditional statements in php are if else, switch and ternary operator. Let me introduce these conditions to you. Some syntax of statements. The basic syntax structure of if single branch if (conditional expression) {...