PHP Check if Variable Exists

We should verify the existence of variables before using them to avoid unexpected errors or behavior. If we check exactly whether the variable exists, it can help to improve the reliability, and security of your PHP applications. So, in this article, we will see how to check if the variable exists or not in PHP.

Before we create a variable we need to check if the variable already exists. If not checked, the value of the existing variable is also likely to change

Why should we check if variable exists in PHP?

• You can prevent these errors from occurring, by improving the robustness and reliability of your code by checking if a variable exists before using it.
• This helps ensure that your code handles both expected and unexpected scenarios gracefully, reducing the risk of security vulnerabilities or unexpected behavior.
• It allows you to incorporate conditional logic based on whether the variable is present or not.

3 Best ways to check if variable exist

You can use these ways to check if the variable exists or not in PHP.

1. isset() function

In this method, we have to use the ‘isset()’ function in the if statement and pass the variable we want to check as an argument.

Syntax:

if (isset($variable)) {
  // Variable exists
} else {
  // Variable does not exist
}

Example:

$data = "john";

if (isset($data)) {
  // Variable exists
  echo "Variable exists";
} else {
  // Variable does not exist
  echo "Variable does not exist";
}

//Output : Variable exists

In this above code, we have created the variable ‘data’ and assigned it to the string value “john”. Then we check if variable ‘data’ is exist or not using the ‘isset()’ function in the if statement and pass variable ‘data’ as an argument. It returns ‘variable exists’, because the variable is already created.

2. empty() function

In this method, we have to use the ’empty()’ function in the if statement and pass the variable we want to check as an argument.

Syntax:

if (!empty($variable)) {
  // Variable exists
} else {
  // Variable does not exist
}

Example:

$data = "john";

if (!empty($variable)) {
  // Variable exists
  echo "Variable exists";
} else {
  // Variable does not exist
  echo "Variable does not exist";
}

//Output : Variable exists

In this above code, we have created the variable ‘data’ and assigned it to the string value “john”. Then we check if the variable exists or not using the ’empty()’ function in the if statement and pass the variable ‘data’ as an argument. It returns ‘variable exists’ because the variable is already created. If a variable is not created, then it returns ‘variable does not exist’.