Passing a String's True/False Boolean Value into a Functions Argument

问题

Thank you so much for reading and responding if you can.

In one function I test a condition and make a string 'true' or 'false', which then I make a global variable.
Then I call another function with that string as the parameter

Within that function's if statement, I want to test based off the strings boolean value of 'true' or 'false'

$email_form_comments = $_POST['comments']; // pull post data from form

if ($email_form_comments) $comments_status = true;  // test if $email_form_comments is instantiated. If so, $comments_status is set to true
else $error = true; // if not, error set to true. 

test_another_condition($comments_status); // pass $comments_status value as parameter 

function test_another_condition($condition) {

    if($condition != 'true') {    // I expect $condition to == 'true'parameter
      $output = "Your Condition Failed";
      return $output;
     }

}

My thinking is that $condition will hold a 'true' value, but this is not so.

回答1:

I think the key here is PHP will evaluate empty strings as false and non-empty strings as true, and when setting and comparing booleans make sure to use constants without quotes. Use true or false not 'true' or 'false'. Also, I suggest writing your if statements so they will set alternate values on a single variable, or in the case of a function return an alternate value when the condition fails.

I made some small modifications to your code so that your function will evaluate true

// simulate post content
$_POST['comments'] = 'foo'; // non-empty string will evaluate true
#$_POST['comments'] = ''; // empty string will evaluate false

$email_form_comments = $_POST['comments']; // pull post data from form

if ($email_form_comments) {
  $comments_status = true;  // test if $email_form_comments is instantiated. If so, $comments_status is set to true
} else {
  $comments_status = false; // if not, error set to true. 
}

echo test_another_condition($comments_status); // pass $comments_status value as parameter 

function test_another_condition($condition)
{
    if ($condition !== true) { 
      return 'Your Condition Failed';
    }

    return 'Your Condition Passed';
}

来源：https://stackoverflow.com/questions/34298241/passing-a-strings-true-false-boolean-value-into-a-functions-argument

标签

php

boolean

parameter-passing