How to Check Type and Value of Null in PHP

1. Compare Null Value With Empty String Using Double and Triple Equals Operator in PHP
2. Compare Null Value With 0 Using Double and Triple Equals Operator in PHP
3. Compare Null Value With false Using Double and Triple Equals Operator in PHP

This article will compare and check the PHP null value with values like '', 0, and false. We will use the double and triple equals operator to demonstrate the differences.

Compare Null Value With Empty String Using Double and Triple Equals Operator in PHP

In PHP, there are various comparison operators. We use the comparison operators to compare the value between two entities. The double and triple equals operators in PHP are most commonly used. There is a simple difference between these two comparison operators. The double equals operator, == compares the value between the two entities. Whereas the triple equals operator, === compares the value, as well as the type between the two entities. We need to know these differences to compare the entities in PHP the way we want.

We can compare a null value with an empty string and watch the differences using these, both comparison operators. For example, create a variable $foo and assign it to an empty string. Then, compare the variable with NULL with the double equals operator using the if condition. Display the message foo is null, if the condition is true. Display the message the condition is false, if the condition is false. Similarly, use the triple equals operator for the same piece of code.

We can see that the first code example returns the true value, and the second returns the false value. The double equals operator compares only the value of empty string and NULL, and the value are equal. But, the triple equals operator compares the value as well as the type of these entities. As the empty string is of string type and NULL is of NULL type, the value returned is false. We can use the gettype() function to check the type.

Example Code:

$foo = '';
if($foo == NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

foo is null

Example Code:

$foo = '';
if($foo === NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

the condition is false

Compare Null Value With 0 Using Double and Triple Equals Operator in PHP

Here, we will compare NULL with 0 using the double equals and triple equals operator. We know that 0 is an integer. When we compare it with NULL using the double equals operator, the condition will be true as 0 is null. But, integer and NULL are different types. Therefore, using the triple equals operator will run the false condition.

Thus, we learned how the double and triple equals comparison operators work while comparing the null value with 0.

Example Code:

$foo = 0;
if($foo == NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

foo is null

Example Code:

$foo = 0;
if($foo === NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

the condition is false

Compare Null Value With false Using Double and Triple Equals Operator in PHP

We will compare NULL with the false boolean value using the double and triple equals comparison operators. The value of false and NULL are the same; therefore, the true condition is executed using the double equals operator. As false is a boolean value, its type is not the same as NULL, so the false condition is executed.

Example Code:

$foo = false;
if($foo == NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

foo is null

Example Code:

$foo = false;
if($foo === NULL) {
 echo 'foo is null';
}
else{
 echo 'the condition is false';
}

Output:

the condition is false