ArrayAccess::offsetExists

(No version information available, might be only in CVS)

ArrayAccess::offsetExists — Whether a offset exists

说明

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

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.

参数

offset: An offset to check for.

返回值

如果成功则返回 TRUE，失败则返回 FALSE。

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

范例

Example #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"]));
?>

上例的输出类似于：

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)