$string = "Welcome to plus2net.com";
var_dump(filter_var($string, FILTER_VALIDATE_REGEXP,
array("options"=>array("regexp"=>"/^W(.*)/"))))
Output is
string(23) "Welcome to plus2net.com"
By using FILTER_VALIDATE_REGEXP we can validate Regular expression .
Change the $string variable value to
$string="ZWelcome to plus2net.com";
Output is now
bool(false)
Example 2
$string = "Welcome to plus2net.com"; // change the first char and see the result
if(filter_var($string, FILTER_VALIDATE_REGEXP,array("options"=>array("regexp"=>"/^W(.*)/")))){
echo "yes Cleared ";
}else{
echo " No not cleared ";
}