PHP Resources

PHPServer Side ProgrammingProgramming

Definition and Usage

In PHP, Resource  is a special data type that refers to any external resource. A resource variable acts as a reference to external source of data such as stream, file, database etc. PHP uses relevent functions to create these resources. For example, fopen() function opens a disk file and its reference is stored in a resource variable.

PHP's Zend engine uses reference conting system. As a result, a resource with zero reference count is destroyed automatically by garbage collector. Hence, memory used by resource data type need not be freed manually.

Various types of resources can be handled in a PHP script, with the help of coresponding functions. Following table shows a select list −

Resource Type Name
Created By
Destroyed By
Definition
bzip2
bzopen()
bzclose()
Bzip2 file
curl
curl_init()
curl_close()
Curl session
ftp
ftp_connect(),
ftp_close()
FTP stream
mssql link
mssql_connect()
mssql_close()
Link to Microsoft SQL Server database
mysql link
mysql_connect()
mysql_close()
Link to MySQL database
mysql result
mysql_db_query(),
mysql_free_result()
MySQL result
oci8 connection
oci_connect()
oci_close()
Connection to Oracle Database
ODBC link
odbc_connect()
odbc_close()
Link to ODBC database
pdf document
pdf_new()
pdf_close()
PDF document
stream
opendir()
closedir()
Dir handle
stream
fopen(), tmpfile()
fclose()
File handle
socket
 
fclose()
Socket handle
xml
xml_parser_create(),
xml_parser_free()
XML parser
zlib
gzopen()
gzclose()
gz-compressed file
zlib.deflate
deflate_init()
None()
incremental deflate context
zlib.inflate
inflate_init()
None()
incremental inflate context

In this context, PHP has get_resource_type() function that returns resource type of a variable.

Syntax

To declare an object of a class we need to use new statement

get_resource_type ( resource $handle ) : string

where $handle is the resource variable whose type is to be obtained. This function returns a string corresponding to resource type

Following example shows resource type of a disk file

Example

 Live Demo

<?php
$fp=fopen("test.txt","w");
var_dump($fp);
?>

Output

This will produce following result −

resource(5) of type (stream)

Following example uses get_resource_type() function

Example

 Live Demo

<?php
$fp = fopen("test.txt", "w");
echo get_resource_type($fp) . "\n";
?>

Output

This will produce following result −

stream
raja
Published on 19-Sep-2020 18:23:19
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