Issue with PHP Preg_Match

Question

I'm working on a CodeIgniter project, and I'm making a custom validation, and I'm no regex expert. So far, I have made a simple test, but I cannot seem to get this right. This validation can only contain A-Z a-z 0-9 and special characters such as:

@ ! # / $ % & ' * + - = ? ^ _ ` { | } ~ .

I cannot have ( ) [ ] : ; " < > , \

in my controller:

public function test(){

 $this->form_validation->set_rules('communication_number', 'Communication Number', 'required|trim|xss_clean|callback_validate_communication_number');

    $this->form_validation->set_message("validate_communication_number", "The %s field must only contain blah blah");

    if($this->form_validation->run() == false)
    {
        echo validation_errors();
    }
    else
    {
        echo "Passed";
    }
}

public function validate_communication_number($communication_number)
{
    if(preg_match("/^[a-z0-9@\!\#\/$\%\&\'\*\+\-\/\=\?/^/_/`/{/|/}/~/.]+$/i", $communication_number))
    {
        return true;
    }
    else
    {
        return false;
    }
}

Answer 1

You have to escape backslashes using \\ if you use double quotes or just change to single quote like this:

if(preg_match('/^[a-z0-9@\!\#\/$\%\&\'\*\+\-\/\=\?/^/_/`/{/|/}/~/.]+$/i', $ff_communication_room))
              ^--- Here

However, you can write your regex as this (you don't need all those escaped backslashes:

^[a-z0-9@!#\/$%&'*+=?^_`{|}~.-]+$

As you can see, it's a valid regex:

Working demo

Code

$re = '/^[a-z0-9@!#\/$%&'*+=?^_`{|}~.-]+$/i'; // Note hyphen at the end
$str = "your string"; 

if(preg_match($re, $str))
{
    return true;
}
else
{
    return false;
}