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Usage and Examples of PHP openssl_pkey_export_to_file() Function

PHP OpenSSL Function Manual

The openssl_pkey_export_to_file() function is used to export the key to a file.

Definition and Usage

openssl_pkey_export_to_file()The function exports the key to a file.

The openssl_pkey_export_to_file() function saves the key in PEM format, where PEM stands for Privacy Enhanced Mail.-Enhanced Mail, mainly used for storing encrypted keys and certificates.

Syntax

openssl_pkey_export_to_file ( mixed $key , string $outfilename [, string $passphrase [, array $configargs ] ] ) : bool

Parameters

Serial number	Parameters	Description
1	key	The key to be exported to the file.
2	outfilename	outfilename is the path to save the .pem file.
3	passphrase	Password that can be used to protect the file.
4	configargs	The parameter configargs is required to be provided to the function to generate the private key/The detailed configuration information for the public key pair, as described below.

Configuration parameters

By default, openssl_pkey_new() uses the detailed configuration information that exists in openssl.cnf. However, configargs can override them. The detailed configuration information is as follows:

configargs	Type	Keys used in openssl.conf	Description
digest_alg	String	default_md	The digest method you obtain from openssl_get_md_methods().
x509_extensions	String	x509_extensions	Create x509The extension name used when creating a certificate.
req_extensions	String	req_extensions	The extension name used when creating CSR.
private_key_bits	integer	default_bits	Specify the number of bits to be used when generating the private key.
private_key_type	integer	none	The type of private key to be created. It can be one of OPENSSL_KEYTYPE_DSA, OPENSSL_KEYTYPE_DH, OPENSSL_KEYTYPE_RSA, or OPENSSL_KEYTYPE_EC. The default value is OPENSSL_KEYTYPE_RSA.
encrypt_key	Boolean	encrypt_key	Is the exported key encrypted?
encrypt_key_cipher	integer	none	Password constants, such as OPENSSL_CIPHER_RC2_40 (integer), OPENSSL_CIPHER_RC2_128(integer), OPENSSL_CIPHER_RC2_64(integer), OPENSSL_CIPHER_DES (integer), OPENSSL_CIPHER_3DES (integer) and others.
curve_name	String	none	One of the curve names returned by the openssl_get_curve_names() function.
config	String	N/A	You can change the configuration in openssl.conf as needed and provide its path here.

Return value

If the PHP openssl_pkey_export_to_file() function succeeds, it returns true; otherwise, it returns false.

PHP version

This function will start from versions greater than5Starting from PHP version .0.0

Instance1

The function of openssl_pkey_export_to_file()-

Example

<?php
　　　　　　　　//Create private key
	$privkey = openssl_pkey_new();
	openssl_pkey_export_to_file($privkey, 'C:/xampp/htdocs/modules/openssl/keytest.pem');
?>

The detailed information stored in the file keytest.pem is as follows-

Instance2

Obtain the key from the .pem file-

Example

<?php
　　　　　　　　//Create private key
	$privkey = openssl_pkey_new();
	openssl_pkey_export_to_file($privkey, 'C:/xampp/htdocs/modules/openssl/keytest.pem');
	//Use the .pem file with the private key.
	$testprivatekey = openssl_get_privatekey(file_get_contents('C:/xampp/htdocs/modules/openssl/keytest.pem'));
	if ($testprivatekey === false) {
		var_dump(openssl_error_string());
	} else {
		//var_dump($testprivatekey);
		$key_details = openssl_pkey_get_details($testprivatekey);
		print_r($key_details["key"]);	
	}
?>

stored in file test-csr1Detailed information in .pem as follows-

PHP OpenSSL Function Manual

PHP CURL Functions PHP OpenSSL Functions