PHP Variable Handling is_resource() Function

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The PHP Variable Handling is_resource() function is used to checks whether a variable is a resource. In PHP, a resource is a specific type of data, similar to a file handle or a database connection. This function is useful when working with files, databases, and network connections.

Before using a resource, it is a good idea to make that it is still valid. If the variable represents a resource, the function will return true. If the variable isn't a resource, it returns false. It is mainly used for debugging and error checking in PHP programs.

Syntax

Below is the syntax of the PHP Variable Handling is_resource() function −

bool is_resource ( mixed $value )

Parameters

This function accepts $value parameter which is the variable to be evaluated.

Return Value

The is_resource() function returns TRUE if value is a resource, FALSE otherwise.

PHP Version

First introduced in core PHP 4, the is_resource() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

This program checks if a file handle is a resource with the help of the PHP Variable Handling is_resource() function. It opens a file and checks if the file handle is a valid resource.

<?php
   // Open a file and get the resource
   $file = fopen("/PHP/PhpProjects/myfile.txt", "r"); 

   // Check if $file is a resource
   if (is_resource($file)) {
      echo "The variable is a resource.";
   } else {
      echo "The variable is not a resource.";
   }

   // Close the file
   fclose($file);
?>

Output

Here is the outcome of the following code −

The variable is a resource.

Example 2

In the below PHP code we will use the is_resource() function and check for an invalid resource. This program tries to open a file which is not present. So the is_resource() function will return false if the file handle is invalid.

<?php
   // Try to open a file which is not present
   $file = @fopen("file_not_present.txt", "r"); 

   // Check if $file is a resource
   if (is_resource($file)) {
      echo "The variable is a resource.";
   } else {
      echo "The variable is not a resource.";
   }
?> 

Output

This will generate the below output −

The variable is not a resource.

Example 3

Now the below code checks a socket connection is a valid resource or not using the is_resource() function. So the program basically creates a socket connection and checks if it is a resource.

<?php
   // Create a socket
   $socket = stream_socket_client("tcp://www.tutorialspoint.com:80", $errno, $errstr, 30);

   // Check if $socket is a resource
   if (is_resource($socket)) {
      echo "The socket connection is a resource.";
   } else {
      echo "The socket connection is not a resource.";
   }

   // Close the socket
   fclose($socket);
?> 

Output

This will create the below output −

The socket connection is a resource.