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Optimize array_key_exists/in_array for empty array
Make opcache replace the result with false if the array argument is
known to be empty.
This may be useful when a codebase has placeholders,
e.g. `if (!in_array($method, self::ALLOWED_METHODS)) { return; }`
In zend_inference.c: In php 8, array_key_exists will throw
a TypeError instead of returning null.
I didn't see any discussion of this optimization (for/against)
after a quick search on github, e.g. phpGH-3360
Potential future optimizations:
- convert `in_array($needle, ['only one element'], true)` to `===`?
(or `==` for strict=false)
- When the number of elements is less than 4, switch to looping instead of hash
lookup. (exact threshold for better performance to be determined)
Also support looping for `in_array($value, [false, 'str', 2.5], true/false)`- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,46 @@ | ||
| --TEST-- | ||
| array_key_exists() on known empty array | ||
| --EXTENSIONS-- | ||
| opcache | ||
| --FILE-- | ||
| <?php | ||
| error_reporting(E_ALL); | ||
| function helper(&$var) { | ||
| var_dump($var); | ||
| } | ||
| class ExampleArrayKeyExists { | ||
| const EMPTY_ARRAY = []; | ||
| public static function test(int $x, array $arr) { | ||
| $y = array_key_exists($x, self::EMPTY_ARRAY); | ||
| $v2 = array_key_exists($undef, self::EMPTY_ARRAY); | ||
| $z = array_key_exists($x, []); | ||
| $z1 = array_key_exists($x, [1 => true]); | ||
| $z2 = array_key_exists($x, [2 => true]); | ||
| $w = array_key_exists('literal', self::EMPTY_ARRAY); | ||
| echo helper($y); | ||
| echo helper($z); | ||
| echo helper($w); | ||
| echo helper($z1); | ||
| echo helper($z2); | ||
| $unusedVar = array_key_exists('unused', $arr); | ||
| if (array_key_exists(printf("Should get called\n"), self::EMPTY_ARRAY)) { | ||
| echo "Impossible\n"; | ||
| } | ||
| $v = array_key_exists($arr, self::EMPTY_ARRAY); | ||
| } | ||
| } | ||
| try { | ||
| ExampleArrayKeyExists::test(1,[2]); | ||
| } catch (TypeError $e) { | ||
| printf("%s at line %d\n", $e->getMessage(), $e->getLine()); | ||
| } | ||
| ?> | ||
| --EXPECTF-- | ||
| Warning: Undefined variable $undef in %s on line 10 | ||
| bool(false) | ||
| bool(false) | ||
| bool(false) | ||
| bool(true) | ||
| bool(false) | ||
| Should get called | ||
| Illegal offset type at line 24 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,51 @@ | ||
| --TEST-- | ||
| in_array() on known empty array | ||
| --EXTENSIONS-- | ||
| opcache | ||
| --FILE-- | ||
| <?php | ||
| error_reporting(E_ALL); | ||
| function helper(&$var) { | ||
| var_dump($var); | ||
| } | ||
| class ExampleInArray { | ||
| const EMPTY_ARRAY = []; | ||
| public static function test(int $x, array $arr) { | ||
| $y = in_array($x, self::EMPTY_ARRAY); | ||
| $y2 = in_array($x, self::EMPTY_ARRAY, true); | ||
| $v2 = in_array($undef, self::EMPTY_ARRAY); | ||
| $z = in_array($x, []); | ||
| $w = in_array('literal', self::EMPTY_ARRAY); | ||
| $z1 = in_array($x, [1]); | ||
| $z2 = in_array($x, [2]); | ||
| $z3 = in_array($x, [1], true); | ||
| $z4 = in_array($x, [2], true); | ||
| echo helper($y); | ||
| echo helper($y2); | ||
| echo helper($z); | ||
| echo helper($w); | ||
| echo "Results for non-empty arrays\n"; | ||
| echo helper($z1); | ||
| echo helper($z2); | ||
| echo helper($z3); | ||
| echo helper($z4); | ||
| $unusedVar = in_array('unused', $arr); | ||
| if (in_array(printf("Should get called\n"), self::EMPTY_ARRAY)) { | ||
| echo "Impossible\n"; | ||
| } | ||
| } | ||
| } | ||
| ExampleInArray::test(1,[2]); | ||
| ?> | ||
| --EXPECTF-- | ||
| Warning: Undefined variable $undef in %s on line 11 | ||
| bool(false) | ||
| bool(false) | ||
| bool(false) | ||
| bool(false) | ||
| Results for non-empty arrays | ||
| bool(true) | ||
| bool(false) | ||
| bool(true) | ||
| bool(false) | ||
| Should get called |