【PHP】function加減乘除

表單↓

<form name="form1" method="post" action="math.php">

<input type="text" name="value1" required>
<select name="symbol" required> 
	<option value="">請選擇</option>
	<option value="+">+</option>
	<option value="-">-</option>
	<option value="*">*</option>
	<option value="/">/</option>
</select>
<input type="text" name="value2" required>
<input type="submit" value="計算">

</form>

PHP↓

<?php


//A.除錯isset(為了看輸入值是否為空)
if(isset($_POST['symbol'])){$symbol=$_POST['symbol'];}//加減乘除
if(isset($_POST['value1'])){$value1=$_POST['value1'];}
if(isset($_POST['value2'])){$value2=$_POST['value2'];}

//B.主要計算程式
function opration($symbol,$value1,$value2) { //有這三種變數

	if($symbol=="+"){ $result=$value1+$value2;}
	elseif($symbol=="-"){ $result=$value1-$value2;}
	elseif($symbol=="*"){ $result=$value1*$value2;}
	elseif($symbol=="/"){ $result=$value1/$value2;}
	else { $result="錯誤";}
	
	echo $result;
}

//C.如果三個值都存在則計算,否則顯示"錯誤"
if(isset($symbol) && isset($value1) && isset($value2)){
opration($symbol,$value1,$value2);//計算
}else{
	echo "錯誤"; 
}

//opration("*",2,3) //函數驗算程式,自己帶入數值

?>