Object Storage Service:Determine whether a file exists (PHP SDK V2)

Prerequisites

• The sample code in this topic uses the China (Hangzhou) region as an example. The region ID is cn-hangzhou. By default, a public endpoint is used. To access OSS from other Alibaba Cloud services in the same region, use an internal endpoint. For more information about the regions and endpoints that OSS supports, see OSS regions and endpoints.

• To download a file, you must have the oss:GetObject permission. For more information, see Grant a custom access policy to a RAM user.

Sample code

You can use the following code to determine whether a file exists.

<?php

// Import the autoloader file to ensure that dependency libraries are correctly loaded.
require_once __DIR__ . '/../vendor/autoload.php';

use AlibabaCloud\Oss\V2 as Oss;

// Define the description of command line arguments.
$optsdesc = [
    "region" => ['help' => 'The region in which the bucket is located.', 'required' => True], // The region where the bucket is located. (Required)
    "endpoint" => ['help' => 'The domain names that other services can use to access OSS.', 'required' => False], // The endpoint. (Optional)
    "bucket" => ['help' => 'The name of the bucket', 'required' => True], // The name of the bucket. (Required)
    "key" => ['help' => 'The name of the object', 'required' => True], // The name of the object. (Required)
];

// Transform the argument descriptions into the long option format required by getopt.
// A colon (:) after each argument indicates that the argument requires a value.
$longopts = \array_map(function ($key) {
    return "$key:";
}, array_keys($optsdesc));

// Parse the command line arguments.
$options = getopt("", $longopts);

// Authenticate whether the required parameters are specified.
foreach ($optsdesc as $key => $value) {
    if ($value['required'] === True && empty($options[$key])) {
        $help = $value['help']; // Obtain the help information of the parameter.
        echo "Error: the following arguments are required: --$key, $help" . PHP_EOL;
        exit(1); // If a required parameter is missing, exit the program.
    }
}

// Fetch values from the parsed parameters.
$region = $options["region"]; // The region where the bucket is located.
$bucket = $options["bucket"]; // The name of the bucket.
$key = $options["key"];       // The name of the object.

// Load the credentials from environment variables.
// Use EnvironmentVariableCredentialsProvider to read the Access Key ID and Access Key Secret from environment variables.
$credentialsProvider = new Oss\Credentials\EnvironmentVariableCredentialsProvider();

// Use the default configurations of the SDK.
$cfg = Oss\Config::loadDefault();
$cfg->setCredentialsProvider($credentialsProvider); // Set the credentials provider.
$cfg->setRegion($region); // Set the region where the bucket is located.
if (isset($options["endpoint"])) {
    $cfg->setEndpoint($options["endpoint"]); // If an endpoint is provided, set the endpoint.
}

// Create an OSS client instance.
$client = new Oss\Client($cfg);

// Check whether the object exists.
$exist = $client->isObjectExist(bucket: $bucket, key: $key);

// Print the check result.
printf(
    'object is exist:' . var_export($exist, true) . PHP_EOL // Output the Boolean value that indicates whether the object exists.
);

References

• For the complete sample code that is used to determine whether a file exists, see GitHub sample.

• For more information about the API operation that is used to determine whether a file exists, see IsObjectExist.