PHP 7.2.0 Alpha 2 Released

is_resource

(PHP 4, PHP 5)

is_resource Verifica se una variabile รจ una risorsa

Descrizione

bool is_resource ( mixed $var )

Verifica se una data variabile sia di tipo risorsa.

Elenco dei parametri

var

La variabile da valutare.

Valori restituiti

Restituisce TRUE se la variabile individuata dal parametro var รจ di tipo resource, altrimenti restituisce FALSE.

Esempi

Example #1 Esempio di utilizzo di is_resource()

<?php

$db_link 
= @mysql_connect('localhost''mysql_user''mysql_pass');
if (!
is_resource($db_link)) {
    die(
'Can\'t connect : ' mysql_error());
}

?>

Vedere anche:

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User Contributed Notes 2 notes

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14
btleffler [AT] gmail [DOT] com
6 years ago
I was recently trying to loop through some objects and convert them to arrays so that I could encode them to json strings.

I was running into issues when an element of one of my objects was a SoapClient. As it turns out, json_encode() doesn't like any resources to be passed to it. My simple fix was to use is_resource() to determine whether or not the variable I was looking at was a resource.

I quickly realized that is_resource() returns false for two out of the 3 resources that are typically in a SoapClient object. If the resource type is 'Unknown' according to var_dump() and get_resource_type(), is_resource() doesn't think that the variable is a resource!

My work around for this was to use get_resource_type() instead of is_resource(), but that function throws an error if the variable you're checking isn't a resource.

So how are you supposed to know when a variable is a resource if is_resource() is unreliable, and get_resource_type() gives errors if you don't pass it a resource?

I ended up doing something like this:

<?php

function isResource ($possibleResource) { return !is_null(@get_resource_type($possibleResource)); }

?>

The @ operator suppresses the errors thrown by get_resource_type() so it returns null if $possibleResource isn't a resource.

I spent way too long trying to figure this stuff out, so I hope this comment helps someone out if they run into the same problem I did.
up
4
CertaiN
3 years ago
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
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