php if else swicth conditional control statement study notes_PHP tutorial

The most commonly used conditional control statements in PHP are if else or switch statements. Now I will give you a detailed introduction to my notes on using if else conditional control statements in PHP. Friends in need can refer to them.

In the PHP language, the basic process control structures are: sequential structure, branch structure, and loop structure.

Commonly used control statements mainly include:

if, if...else judgment statements
switch branch statement
while, do...while loop statement
for loop statement
break, continue interrupt statements

The php if statement is a simple judgment statement, which implements the function of conditional judgment. When the program executes a statement and encounters a fork in the road, it selects and executes the corresponding statement by judging whether the value of the statement meets the conditions. So the if statement is the most basic PHP conditional expression.

The basic structure is:

if (judgment statement)

{

Execution statement body

}

Example:

The code is as follows

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代码如下	复制代码
$a=8;  $b=4;  if($a>$b){  /* 若$a>$b，则执行大括号内的执行语句 */   $a++;  }  $c=$a+$b;  echo "a+b=".$c; ?>

$a=8; $b=4;

if($a>$b){ /* If $a>$b, execute the execution statement within the curly brackets */

$a++;

}

$c=$a+$b;

echo "a+b=".$c;

?>

The if statement can choose whether to execute the statement body, while the if...else statement is a choice of two. You must choose one of the two statement bodies to execute. It can be interpreted as "what to do if something happens, otherwise how to solve it", so if...else is essentially a selective statement.

If the value is non-0 (i.e. true), then statement body 1 is executed, and if the value is 0 (i.e. false), then statement body 2 is executed.

The basic structure of the if...else statement is:

if (judgment statement)

{

Execute statement body 1

}

else

代码如下	复制代码
$a=11;  $b=9;  if($a>$b){   $c=$a+$b;  }  else{   $c=$a-$b;  }  echo $c; ?>

{

Execute statement body 2

}

Example:

The code is as follows	Copy code
$a=11; $b=9; if($a>$b){ $c=$a+$b; } else{ $c=$a-$b; } echo $c; ?>

代码如下	复制代码
$score=61;  if($score >=90){   echo "成绩优秀";  }  else if($score >=60){   echo "及格.";  }  else if($score   不及格;  }  else echo "成绩有误"; ?>

The if...else statement can only implement two-way branches. To achieve multiple branches, just use multiple if...else statements to nest. Its structural form is as follows: if(judgment statement 1){ Execute statement body 1 } else if(judgment statement 2){ Execute statement body 2 } else if… else… Example:

The code is as follows	Copy code
$score=61; if($score >=90){ echo "Excellent results"; } else if($score >=60){ echo "passed."; } else if($score Failed; } else echo "Wrong results"; ?>

Multiple if() statements can be nested in the if statement to realize the judgment of multiple parameters. It is generally called multiple nesting of if statements. Its basic structural form is as follows:

if(judgment 1)

if(judgment 2) statement body 1

else statement body 2

else

…

You should pay attention to the pairing relationship between if and else here. Starting from the inner layer, else is always paired with the nearest if above it. Be particularly careful when programming.

Example:

The code is as follows

代码如下	复制代码
$gender="女性";  $age=28;  if($gender=="男性"){   if($age >=18){    echo "你是个男人";   }   else if($age    echo "你是个男孩";   }  }  else{   if($age >=18){    echo "你是个女人";   }   else if($age    echo "你是个女孩";   }  } ?>

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$gender="female"; $age=28;

if($gender=="male"){
if($age >=18){
echo "You are a man";
}
else if($age echo "You are a boy";
}
}
else{
if($age >=18){
echo "You are a woman";
}
else if($age echo "You are a girl";

}

}

代码如下	复制代码
$i=0;  switch($i){   case(0):    echo "you are a girl ";    break;   case(1):    echo "you are a boy ";    break;   default:    echo "it's an animal";   } ?>

?>

As introduced earlier, the if...else nested structure can realize the function of multi-branch selection, but the code of this method is relatively lengthy. To realize the function of multi-branch selection, PHP also provides switch statements. Using the switch statement makes the script more concise. Basic structure: switch(expression){ case 1: Execution statement body 1; break; case 2: Execution statement body 2; break; ... default:

Execution statement body n; break; }

The value of the expression is first matched with the case statement one by one. If there is a match, the statement body is executed, and then the loop is jumped out. If no case statement is matched in the end, the execution statement after default is executed.

Example:

The code is as follows

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$i=0; switch($i){ case(0): echo "you are a girl "; Break; case(1): echo "you are a boy "; Break; default: echo "it's an animal"; } ?> http://www.bkjia.com/PHPjc/628841.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/628841.htmlTechArticleThe most commonly used conditional control statements in PHP are if else or switch statements. Let me introduce them in detail below. My notes on using if else conditional control statements in php. Friends in need...