(PHP 5, PHP 7)
ArrayObject::offsetExists — Returns whether the requested index exists
public ArrayObject::offsetExists ( mixed $index ) : bool
index
The index being checked.
 true if the requested index exists, otherwise false 
Example #1 ArrayObject::offsetExists() example
<?php
$arrayobj = new ArrayObject(array('zero', 'one', 'example'=>'e.g.'));
var_dump($arrayobj->offsetExists(1));
var_dump($arrayobj->offsetExists('example'));
var_dump($arrayobj->offsetExists('notfound'));
?> The above example will output:
bool(true) bool(true) bool(false)
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    https://www.php.net/manual/en/arrayobject.offsetexists.php