ตรวจสอบ Expession ของ คณิตศาสตร์ อยากตรวจสอบพวก [{(2+8)}] --> ถูก [[2+8) -->ผิด ประมาณนี้หนะครับ

<?php
$text = $_REQUEST['m'];
function transformStr($texp)
{
$text = strrev($text) ;
for($i=0 ; $i<strlen($text) ; $i++)
{
if( $text[$i] == ")")
$text[$i] = "(" ;
else if( $text[$i] == "}")
$text[$i] = "{" ;
else if( $text[$i] == "]")
$text[$i] = "[" ;

}
return  $text;
}
$result = "Not Correct" ;
for( $i=0 ; $i<strlen($text) ; $i++)
{
if( $text[$i] == "[" or $text[$i] == "{"  or $text[$i] == "("  ) 
$l = $l.$text[$i] ;
else if( $text[$i] == "]" or $text[$i] == "}"  or $text[$i] == ")"  ) 
$r = $r.$text[$i] ;
}
if(strlen( $l ) == strlen($r) )
{
if( strcmp($l, transformStr($r)) == 0  ) 
$result ="Correct" ;
}
?>