ArrayAccess::offsetExists

(PHP 5, PHP 7, PHP 8)

ArrayAccess::offsetExistsWhether an offset exists

Description

public ArrayAccess::offsetExists(mixed $offset): bool

Whether or not an offset exists.

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

Note:

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

Parameters

offset

An offset to check for.

Return Values

Returns true on success or false on failure.

Note:

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

Examples

Example #1 ArrayAccess::offsetExists() example

<?php
class obj implements ArrayAccess {
public function
offsetSet($offset, $value): void {
var_dump(__METHOD__);
}
public function
offsetExists($var): bool {
var_dump(__METHOD__);
if (
$var == "foobar") {
return
true;
}
return
false;
}
public function
offsetUnset($var): void {
var_dump(__METHOD__);
}
#[
\ReturnTypeWillChange]
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"]));
?>

The above example will output something similar to:

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
9 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
4 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
5 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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