<p>Using PHP, what's the fastest way to convert a string like this: <code>"123"</code> to an integer?</p>

<p>Why is that particular method the fastest? What happens if it gets unexpected input, such as <code>"hello"</code> or an array?</p>

I've just set up a quick benchmarking exercise:
```
```
Function             time to run 1 million iterations
--------------------------------------------
(int) "123":                0.55029
intval("123"):              1.0115  (183%)

(int) "0":                  0.42461
intval("0"):                0.95683 (225%)

(int) int:                  0.1502
intval(int):                0.65716 (438%)

(int) array("a", "b"):      0.91264
intval(array("a", "b")):    1.47681 (162%)

(int) "hello":              0.42208
intval("hello"):            0.93678 (222%)
```
```
On average, calling intval() is two and a half times slower, and the difference is the greatest if your input already is an integer.
I'd be interested to know
why
though.
Update: I've run the tests again, this time with coercion
```
(0 + $var)
```
```
```
| INPUT ($x)      |  (int) $x  |intval($x) |  0 + $x   |
|-----------------|------------|-----------|-----------|
| "123"           |   0.51541  |  0.96924  |  0.33828  |
| "0"             |   0.42723  |  0.97418  |  0.31353  |
| 123             |   0.15011  |  0.61690  |  0.15452  |
| array("a", "b") |   0.8893   |  1.45109  |  err!     |
| "hello"         |   0.42618  |  0.88803  |  0.1691   |
|-----------------|------------|-----------|-----------|
```
```
Addendum:
I've just come across a slightly unexpected behaviour which you should be aware of when choosing one of these methods:
```
```
$x = "11";
(int) $x;      // int(11)
intval($x);    // int(11)
$x + 0;        // int(11)

$x = "0x11";
(int) $x;      // int(0)
intval($x);    // int(0)
$x + 0;        // int(17) !

$x = "011";
(int) $x;      // int(11)
intval($x);    // int(11)
$x + 0;        // int(11) (not 9)
```
```
Tested using PHP 5.3.1