How to do "+" symbol to be $y

<?php

$y="+";

$x=(10 $y 10); //$x=(10+10);
echo $x;

?>

PHP:

above is my assume, of course it's error.

i'd like to do a switch "+" "-"
how to fix it, echo $x will be 20

thank you

 

Try the following it will echo 20.

<? 
$x = "10";
$y = "10";
echo ($x + $y); 
?>

Code (markup):

 

$y must be "+"; due to i 'd like to switch
it mean i am just change "+" to be "-"
$x will be 0
if change "+" to be "*"
$x will be 100

 

<?php
$y='+';
$x=0;
switch($y)
{
	case '+':
		$x=10+10;
		break;
	case '*':
		$x = 10 * 10;
		break;
}
echo $x;
?>

Code (markup):

 

Try using eval function that can evaluate string as a php code

$x=eval((10 $y 10));

PHP:

 

thank you
but it seems can't using in my case

if($a+$b)
{
}

PHP:

i'd like to switch
if($a+$b)
{
}
to be below
if($a-$b)
{
}
just change + symbols
but +- seems unable to be variable as far as i know.

 

<?php
$y='*';
$x=eval((10 $y 10));
echo $x;
?>
i am tried it, but can't work.

 

Eval is too heavy. There is a much simpler solution. Use a simple multiplier initialized with 1 (for adding) or -1 (for subtraction).
Example:

<?php

if ($subtract)
 $mul = -1;
else
 $mul= 1;

$x = 10 + $mul*10;
echo $x;

?>

PHP:

 

you're getting your cases mixed up , what you want to do is check $y and then based on that you change the operation appropriately.

 

it should be $x=eval("10 $y 10");