ArrayAccess::offsetExists

(PHP 5 >= 5.0.0)

ArrayAccess::offsetExistsWhether an offset exists

Опис

abstract public boolean ArrayAccess::offsetExists ( mixed $offset )

Whether or not an offset exists.

This method is executed when using isset() or empty() on objects implementing ArrayAccess.

Зауваження:

When using empty() ArrayAccess::offsetGet() will be called and checked if empty only if ArrayAccess::offsetExists() returns TRUE.

Параметри

offset

An offset to check for.

Значення, що повертаються

Повертає TRUE в успішному випадку або FALSE в разі помилки.

Зауваження:

The return value will be casted to boolean if non-boolean was returned.

Приклади

Приклад #1 ArrayAccess::offsetExists() example

<?php
class obj implements arrayaccess {
    public function 
offsetSet($offset$value) {
        
var_dump(__METHOD__);
    }
    public function 
offsetExists($var) {
        
var_dump(__METHOD__);
        if (
$var == "foobar") {
            return 
true;
        }
        return 
false;
    }
    public function 
offsetUnset($var) {
        
var_dump(__METHOD__);
    }
    public function 
offsetGet($var) {
        
var_dump(__METHOD__);
        return 
"value";
    }
}

$obj = new obj;

echo 
"Runs obj::offsetExists()\n";
var_dump(isset($obj["foobar"]));

echo 
"\nRuns obj::offsetExists() and obj::offsetGet()\n";
var_dump(empty($obj["foobar"]));

echo 
"\nRuns obj::offsetExists(), *not* obj:offsetGet() as there is nothing to get\n";
var_dump(empty($obj["foobaz"]));
?>

Наведений вище приклад виведе щось подібне до:

Runs obj::offsetExists()
string(17) "obj::offsetExists"
bool(true)

Runs obj::offsetExists() and obj::offsetGet()
string(17) "obj::offsetExists"
string(14) "obj::offsetGet"
bool(false)

Runs obj::offsetExists(), *not* obj:offsetGet() as there is nothing to get
string(17) "obj::offsetExists"
bool(true)

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User Contributed Notes 3 notes

up
5
driezasson at icloud dot com
7 years ago
Note that even though isset/empty works on classes implementing ArrayAccess, array_key_exists does not. At least not in PHP 5.3.
up
0
Martin Q
2 years ago
It seems that in PHP 7, if this method returns FALSE then offsetGet() will return NULL (in PHP 5, offsetGet() didn't first check what value offsetExists() returned).  So if your code suddenly stops working when you upgrade to PHP 7 make sure that offsetExists() returns a sensible value!
up
0
kgun ! mail ! com
3 years ago
If you care about key-strictness, you may need to use an alternative solution (maybe overriding offsetExists() in subclass(es)). So, offsetExists() acts like array_key_exists() and does not handle the key types. Here;

<?php
$array
= ['one', 'two', 3.=>'boom!'];
$arrayObject = new ArrayObject($array);
$key = '3';
var_dump(array_key_exists($key, $array)); // bool(true)
var_dump(in_array($key, array_keys($array), true)); // bool(false)
var_dump($arrayObject->offsetExists($key)); // bool(true)
var_dump(in_array($key, array_keys($arrayObject->getArrayCopy()), true)); // bool(false)

// @override;
public function offsetExists($key)
{
   
// make a strict check
   
return in_array($key, array_keys($this->getArrayCopy()), true);
}
?>
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