How to check if value is empty in PHP [JSON] - php

Question

I have some JSON parameters, that I want to validate if the value are empty with an IF statement. I have written an IF statement in a function to check, but the IF statement only checks for the parameter, I want to check for the values if they are empty. Please, how do I go about this.
my code
//api.php
$payment_type = $this->validateParameter('payment_type', $this->param['payment_type'], STRING, true);
$date_of_delivery = $this->validateParameter('date_of_delivery', $this->param['date_of_delivery'], STRING, true);
$your_generated_waybill_number = $this->validateParameter('your_generated_waybill_number', $this->param['your_generated_waybill_number'], STRING, true);
"payment_type" - is an example of parameter || "1" - is an example of value
{
"name":"create_insert_new_delivery",
"param":{
"payment_type":"1",
"date_of_delivery":"", //E.g here want to check if the value is empty
"your_generated_waybill_number":"39ei40909444567avaab",
}
}
//rest.php
public function validateParameter($fieldName, $value, $required = true){
if($required == true && empty($value) == true){
$this->throwError(EMPTY_PARAMETER, $fieldName . " parameter is missing"); //HERE check if the parameter is missing and fires error, but I also want to include value check
} else if ($required == true && empty($fieldName) == true){
$this->throwError(API_PARAM_REQUIRED, $fieldName . " value is required");
} else {
} //check when parameter is present but value is empty and leave if it is not required
}

Answer 1

testing your variable should be done by using the identity operator.
if (!$var){}
or
if ($var === null){} //checks by type
or
if (empty($field)){}

Answer 2

With empty() function you check for the value
$str = '';
// or
$str = null;
// or
$str = false;
var_dump(empty($str)) // output => true
To check if a variable is defined you can use isset
http://php.net/manual/ro/function.isset.php

Answer 3

You may make your function a little clearer since the tests you are doing will already return true or false. There is no need to compare them to true.
if ($required AND empty($value)) {
$this->throwError(EMPTY_PARAMETER, $fieldName . " parameter is missing"); //HERE check if the parameter is missing and fires error, but I also want to include value check
} elseif ($required AND empty($fieldName)) {
$this->throwError(API_PARAM_REQUIRED, $fieldName . " is required");
} elseif (!empty($fieldName) AND empty($value)) {
$this->throwError(API_PARAM_REQUIRED, $fieldName . " value is required");
}
}

Answer 4

You're main problem is that you're passing the value (grabbed from the array) to the method and checking that. Because at that point, if the array key is not set, a warning is triggered and the value is coerced to null.
empty(): Will return true when the variable is not set OR if it evaluates to some falsey value (e.g. false, null, [], "", etc)
isset(): Will return true ONLY if the value is not set.
So:
$a = ['one' => false];
empty($a['one']); //true
isset($a['one']); //true
isset($a['two']); //false
So you could edit you validation function like so:
public function validateParameter($fieldName, &$inputArray, $required = true){
if($required){
if(!isset($inputArray[$fieldName])){
$this->throwError(EMPTY_PARAMETER, $fieldName . " parameter is missing");
} else if (empty($inputArray[$fieldName])){
$this->throwError(API_PARAM_REQUIRED, $fieldName . " value is required");
}
} else {
if(!isset($inputArray[$fieldName])){
return null;
}
}
return $inputArray[$fieldName];
}
Note: since you are checking a class attribute $this->param. You may avoid passing the array to the method and just reference $this->param in the function, unless it should be more reusable.
I didn't completely understand you desired result in the missing block, but made a reasonable assumption