Question

I am dynamically creating variable to check the check boxes using loop. Actually the I am creating variable using string that is combination of 1 & 0. viz..1010101000110. Its like this. My string length is 50.

$user_authorisation = fetch_table_user($uid, '1', '12');
for ($j = 0; $j <= 49; $j++) {
    if (substr($user_authorisation, $j, 1) == '1') {
        $user_authorisation_field_ . $j = 'checked="checked"';
    }
}

My error is:
Warning: substr() expects parameter 2 to be long, string given in C:\xampp\htdocs\shadaab\user_auth.php on line 38

Answer 1

They’re right, the best solution is to simply use an array:

    for ($j = 0; $j <= 49; $j++)
        if (substr($user_authorisation, $j, 1) == '1')
            $user_authorisation_field[$j] = 'checked="checked"';

But, specifically your problem lies in how you concatinate your variable: $user_authorisation_field_ . $j

@Dong shows how to do it correctly in his answer.

The reason the concatination is incorrect is because you want to treat "user_authorisation_field_" as a string and combine it with a number, but you are unintentially using it as a variable $user_authorisation_field_ which is UNDEFINED. So what you’re doing is basically evaluates as:

UNDEFINED . 0 = 'string';
UNDEFINED . 1 = 'string';
UNDEFINED . 2 = 'string';

etc. Doesn’t work.