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

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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?

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?

• javascript
• php
• html
• forms
• boolean

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2 Answers 2

Sorted by: Reset to default 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.

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.

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