What is the is_resource method in PHP?

The is_resource method can be used to check if a variable is a resource or not.

Syntax

is_resource(mixed $value): bool

This method returns true if the passed value is a resource. Otherwise, it returns false.

Refer here for the list of resources available in PHP.

For closed resources, the is_resource method returns false.

Code

<?php 
  $test = fopen("foo", "w");
  printIsResource($test);
  $test = tmpfile();
  printIsResource($test);
  fclose($test);
  printIsResource($test);
  $test = false;
  printIsResource($test);
  function printIsResource($test){
    echo "The Value is: ";
    var_dump($test);
    echo "Is Resource: ";
    var_dump(is_resource($test));
    
    echo "---------\n\n";
  }
?>

Explanation

In the code above:

  • We open a file, foo, and call the is_resource method. For this case, we will get true as the result.

  • We use the tmpfile method to create a temporary file and call the is_resource method. For this case, we will get true as the result.

  • Then, we use fclose to close the created temporary file and call the is_resource method again. Now, we will get false as the result because the is_resource method returns false for closed resources.

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