How to pass boolean values between PHP, HTML forms, and Javascript

Question

I have a PHP program that uses HTML forms and uses JavaScript for validation. There's a hidden field in the HTML form containing a boolean value that gets set by PHP, validated on submission by JavaScript, and passed to another PHP page.

When I tried to use PHP booleans to set the value of the HTML field, JavaScript evaluated it as blank, so I used ones and zeros and compared them numerically instead, and now it works fine.

My question is: what is best practice in this scenario? How do I get JavaScript to read a true/false value in my PHP-driven HTML hidden field without using ones and zeros? Or is that just a bad idea altogether?

A Person · Accepted Answer · 2017-04-18 12:20:45Z

15

The good news is that PHP and JavaScript have a similar idea about what values are true and false.

An empty string will be false on both sides. A string with something in it (except 0 in PHP) will be true on both sides.
The number 0 will be false on both sides. All other numbers will be true on both sides.

Since the values of a form will always be strings, as Quentin pointed out in his answer, a good practice might be to use an empty string as false value and something else (e.g. 'true') as true value. But I think your way of using 0 and 1 and testing the numerical values is the safest approach because it isn't misleading. (When someone sees 'true' they might think 'false' would also be usable for a false value.

answered Apr 18, 2017 at 12:20

A Person

1,12210 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Quentin · Accepted Answer · 2017-04-18 12:08:51Z

7

The value of a form control will always be a string.

If you want a boolean, then you have to encode it somehow and then parse it somehow.

Using a 0 or 1 is a perfectly good approach. You could also use true and false (which you could generate using json_encode on the PHP side) and run the value through JSON.parse. There are numerous other options along similar lines.

answered Apr 18, 2017 at 12:08

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

2 Comments

Wijay Sharma Over a year ago

can you write how can we encode strings to boolean in html and then pass the data to php script?

Quentin Over a year ago

@WijaySharma — I did. Read the last paragraph of the answer.

Collectives™ on Stack Overflow

How to pass boolean values between PHP, HTML forms, and Javascript

2 Answers 2

Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related