Using PHP, what's the fastest way to convert a string like this: "123"
to an integer?
Why is that particular method the fastest? What happens if it gets unexpected input, such as "hello"
or an array?
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
I personally feel casting is the prettiest.
$iSomeVar = (int) $sSomeOtherVar;
Should a string like 'Hello' be sent, it will be cast to integer 0. For a string such as '22 years old', it will be cast to integer 22. Anything it can't parse to a number becomes 0.
If you really do NEED the speed, I guess the other suggestions here are correct in assuming that coercion is the fastest.
Run a test.
string coerce: 7.42296099663
string cast: 8.05654597282
string fail coerce: 7.14159703255
string fail cast: 7.87444186211
This was a test that ran each scenario 10,000,000 times. :-)
Co-ercion is 0 + "123"
Casting is (integer)"123"
I think Co-ercion is a tiny bit faster. Oh, and trying 0 + array('123')
is a fatal error in PHP. You might want your code to check the type of the supplied value.
My test code is below.
function test_string_coerce($s) {
return 0 + $s;
}
function test_string_cast($s) {
return (integer)$s;
}
$iter = 10000000;
print "-- running each text $iter times.\n";
// string co-erce
$string_coerce = new Timer;
$string_coerce->Start();
print "String Coerce test\n";
for( $i = 0; $i < $iter ; $i++ ) {
test_string_coerce('123');
}
$string_coerce->Stop();
// string cast
$string_cast = new Timer;
$string_cast->Start();
print "String Cast test\n";
for( $i = 0; $i < $iter ; $i++ ) {
test_string_cast('123');
}
$string_cast->Stop();
// string co-erce fail.
$string_coerce_fail = new Timer;
$string_coerce_fail->Start();
print "String Coerce fail test\n";
for( $i = 0; $i < $iter ; $i++ ) {
test_string_coerce('hello');
}
$string_coerce_fail->Stop();
// string cast fail
$string_cast_fail = new Timer;
$string_cast_fail->Start();
print "String Cast fail test\n";
for( $i = 0; $i < $iter ; $i++ ) {
test_string_cast('hello');
}
$string_cast_fail->Stop();
// -----------------
print "\n";
print "string coerce: ".$string_coerce->Elapsed()."\n";
print "string cast: ".$string_cast->Elapsed()."\n";
print "string fail coerce: ".$string_coerce_fail->Elapsed()."\n";
print "string fail cast: ".$string_cast_fail->Elapsed()."\n";
class Timer {
var $ticking = null;
var $started_at = false;
var $elapsed = 0;
function Timer() {
$this->ticking = null;
}
function Start() {
$this->ticking = true;
$this->started_at = microtime(TRUE);
}
function Stop() {
if( $this->ticking )
$this->elapsed = microtime(TRUE) - $this->started_at;
$this->ticking = false;
}
function Elapsed() {
switch( $this->ticking ) {
case true: return "Still Running";
case false: return $this->elapsed;
case null: return "Not Started";
}
}
}
More ad-hoc benchmark results:
$ time php -r 'for ($x = 0;$x < 999999999; $x++){$i = (integer) "-11";}'
real 2m10.397s
user 2m10.220s
sys 0m0.025s
$ time php -r 'for ($x = 0;$x < 999999999; $x++){$i += "-11";}'
real 2m1.724s
user 2m1.635s
sys 0m0.009s
$ time php -r 'for ($x = 0;$x < 999999999; $x++){$i = + "-11";}'
real 1m21.000s
user 1m20.964s
sys 0m0.007s
(int)
andintval()
can be over 400%! – nickf