Stop duplication of random string during PHP session
I am using the following PHP to generate a few (usually 3) random strings and place them in session variables to use as controls.

    function session_var($type) {
    if ( !isset ( $_SESSION[$type] ) ) {
    $_SESSION[$type] = rand_string( 5 );
    }
    }

    function rand_string( $length ) {
    $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";	
    $size = strlen( $chars );
    $str = '';
    for( $i = 0; $i < $length; $i++ ) {
    $str .= $chars[ rand( 0, $size - 1 ) ];
    }
    return ($str);
    }

How do I eliminate the rare occasion where the same random string might be generated more than once in the same session? I don’t want any of the session variables to be the same. 

Thanks

Stop duplication of random string during PHP session
===

I am using the following PHP to generate a few (usually 3) random strings and place them in session variables to use as controls.

    function session_var($type) {
    if ( !isset ( $_SESSION[$type] ) ) {
    $_SESSION[$type] = rand_string( 5 );
    }
    }

    function rand_string( $length ) {
    $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";	
    $size = strlen( $chars );
    $str = '';
    for( $i = 0; $i < $length; $i++ ) {
    $str .= $chars[ rand( 0, $size - 1 ) ];
    }
    return ($str);
    }

How do I eliminate the rare occasion where the same random string might be generated more than once in the same session? I don’t want any of the session variables to be the same. 

Thanks
