get_resource_type()

(PHP 4 >= 4.0.2, PHP 5, PHP 7)

返回资源（resource）类型

描述

get_resource_type(resource $handle): string

此函数返回一个字符串，用于表示传递给它的resource的类型。如果参数不是合法的resource，将产生错误。

<?php
$c = mysql_connect();
echo get_resource_type($c)."\n";
// 打印：mysql link
$fp = fopen("foo","w");
echo get_resource_type($fp)."\n";
// 打印：file
$doc = new_xmldoc("1.0");
echo get_resource_type($doc->doc)."\n";
// 打印：domxml document
?>

Try this to know behavior:
<?php
function resource_test($resource, $name) {
  echo 
    '[' . $name. ']',
    PHP_EOL,
    '(bool)$resource => ',
    $resource ? 'TRUE' : 'FALSE',
    PHP_EOL,
    'get_resource_type($resource) => ',
    get_resource_type($resource) ?: 'FALSE',
    PHP_EOL,
    'is_resoruce($resource) => ',
    is_resource($resource) ? 'TRUE' : 'FALSE',
    PHP_EOL,
    PHP_EOL
  ;
}
 
$resource = tmpfile();
resource_test($resource, 'Check Valid Resource');
 
fclose($resource);
resource_test($resource, 'Check Released Resource');
 
$resource = null;
resource_test($resource, 'Check NULL');
?>
It will be shown as...
[Check Valid Resource]
(bool)$resource => TRUE
get_resource_type($resource) => stream
is_resoruce($resource) => TRUE
[Check Released Resource]
(bool)$resource => TRUE
get_resource_type($resource) => Unknown
is_resoruce($resource) => FALSE
[Check NULL]
(bool)$resource => FALSE
get_resource_type($resource) => FALSE
Warning: get_resource_type() expects parameter 1 to be resource, null given in ... on line 10
is_resoruce($resource) => FALSE

In PHP5 (on Linux), the above example identifies the "file" handler as a 'stream', not 'file'.
This can be particularly worrisome if you're trying to determine the type of stream using this function.
The alternative is to use <?php stream_get_meta_data() ?>, which returns an array containing "stream_type (string) - a label describing the underlying implementation of the stream."

Furthermore, this function returns 'stream' on php 4.3 on windows & linux.
You if you want to differentiate between a file resource and other stream resources, as stated before stream_get_meta_data() gives you an array which, on my system, contains the following elements which might suggest a file handle:
[wrapper_type] => plainfile
[stream_type] => STDIO
However I've only compared this to a stream from a url, so I include this only as a suggestion.

This function will generate an error and return NULL instead FALSE in the next example:
<?php
$var = 3;
var_dump(get_resource_type($var));
?>