How to convert string to boolean in php

I've defined this function in php

function ifstatement($statement = 'if(10 > 9;1+1;2+2)') {
// $statement = str_replace(' ', '', $statement);

if (strpos($statement, 'if(') > -1) {
   $statement = rtrim(ltrim(str_replace(' ', '', $statement), 'if('), ')');
   $exp = explode(';', $statement);
  if ( $exp[0] ) {
    if (strpos($exp[1], 'if(' )> -1) {
     return ifstatement($exp[1]);
   开发者_如何学编程 } else {
     return 1;
   }
  } else {
  if (strpos($exp[2], 'if(')> -1) {
    return ifstatement($exp[2]);
  } else {
   return 0;
  }
 }
}else{
  echo 'out';
  }
}

the problem is the function always return 1 even if the condition in the if statement in the function argument is false which is tested with

if($exp[0])

it looks like the $exp[0] comes as a string, how can i convent this to be tested as if argument

---

$exp[0] contains 10 > 9 (whatever you have before first ;), so it will evaluate to false only it it's an empty string or '0'. To properly evaluate this you should use the eval() function:

$condition = '10 > 9';
$result = eval('return ' . $condition . ';');

Note: don't ever use eval() in production environment unless you are really sure that your input is harmless and you can't do it another way.

---

$exp[0] = (boolean) $exp[0];

is probably the thing you're looking for

---

Unless you're going to do this properly (with a parser), you're better off making users specify their conditions in multiple fields. One row would have a text field for x, a select field for comparison operator (==,<,>), and another text field for y. Then they can specify whether to match all checks or any checks. When they're broken out like this you'll be able to execute the intended logic without having to implement a new language using strpos and eval, which is total madness.

You can see examples of this type of interface in Thunderbird's message filter editing:

and in iTune's smart playlist editing: