使用eval（） - 函数检查变量

Question

I have a list of variables (var1, var2, ...). Now I'd like to check these variables using several conditions and print out an error message if the condition is true.

As there are many "checks" that should be done I saved the "conditions" in a MySQL-DB (varchar):

condition               errormsg
--------------------------------------------------------
$var1!=1 && $var1!=2    var1 should be 1 or 2
$var1==''               var1 is missing
$var3<0 & $var3>10      var3 should be between 0 and 10

Now I'd like to check these variables using the eval-Function:

$res=mysqli_query($con, "SELECT * FROM conditions");

while($row=mysqli_fetch_object($res)){
 if(eval($row->condition))
  echo $row->errormsg;
}

Can this work or is there a better solution without eval()? Thank you for your help!

Answer 1

Many people suggest to get alternate of this . But if you really need this you can do this way. I don't have your data so I have made this with my own way

 <?php
    $condition = "1!=1";
    //$condition = "1==1";
   $error = "test";
   eval("\$con = $condition ;");
   if($con){
   echo $error;
   }else {
  echo "not found";
  }
?>

Uncomment second line to get another change. Just keep in mind that statement should be complete in eval function.

Live demo : https://eval.in/847626

Pay special attention not to pass any user provided data into it without properly validating it beforehand.