获取阵列的所有键,哪一个具有更好的性能？array_keys还是foreach？我想知道array_keys是否是一个使用foreach循环或for循环的函数来获取密钥..(因为foreach是一种语言结构),所以foreach更好.
但是,我不确定array_keys是否使用foreach循环来获取密钥
那么哪一个更好
foreach ($value as $key => $value) {
$pkey = ':' . $key;
$placeholders[$pkey] = $value;
}
$value = array_keys($placeholders);
要么
$keys = array();
foreach ($value as $key => $value) {
$pkey = ':' . $key;
$placeholders[$pkey] = $value;
$keys[] = $pkey;
}
Riz*_*123 12
性能方面,他们几乎无法真正衡量差异,所以简单地说:过早优化是万恶之源.
使用最可靠,最容易维护,记录和解释的代码.编写代码后,开始对其进行分析,然后考虑优化主要瓶颈.
我使用100'000元素的数组运行两个脚本(在PHP 5.6上)10'000次,平均执行时间约为0.025秒.
SCRIPT1:
<?php
$arr = range(1, 100000);
$keys = array_keys($arr);
?>
SCRIPT2:
<?php
$arr = range(1, 100000);
foreach($arr as $k => $v)
$keys[] = $k;
?>
因此,从性能角度来看,两种方法之间没有真正的区别.
但是如果你看两个脚本,你会发现使用foreach循环你有点编写更多的代码和一个"无用的"循环,你也可以看到这个带有foreach循环的方法然后产生更多的操作码并使得数量几乎翻倍作为方法的操作array_keys():
另外正如@EliasVanOotegem的评论中指出的那样,如果代码生成更多操作码以使其在此处清楚,则并不总是坏事!
SCRIPT1:
number of ops: 8
compiled vars: !0 = $arr, !1 = $keys
line # * op fetch ext return operands
---------------------------------------------------------------------------------
3 0 > SEND_VAL 1
1 SEND_VAL 100000
2 DO_FCALL 2 $0 'range'
3 ASSIGN !0, $0
5 4 SEND_VAR !0
5 DO_FCALL 1 $2 'array_keys'
6 ASSIGN !1, $2
7 > RETURN 1
SCRIPT2:
number of ops: 14
compiled vars: !0 = $arr, !1 = $k, !2 = $v, !3 = $keys
line # * op fetch ext return operands
---------------------------------------------------------------------------------
3 0 > SEND_VAL 1
1 SEND_VAL 100000
2 DO_FCALL 2 $0 'range'
3 ASSIGN !0, $0
5 4 > FE_RESET $2 !0, ->12
5 > > FE_FETCH $3 $2, ->12
6 > OP_DATA ~5
7 ASSIGN !2, $3
8 ASSIGN !1, ~5
6 9 ASSIGN_DIM !3
10 OP_DATA !1, $8
11 > JMP ->5
12 > SWITCH_FREE $2
13 > RETURN 1
我想知道array_keys是否是一个使用foreach循环或for循环的函数
array_keys()不直接使用foreach或for循环,但它也循环遍历数组.您可以在源代码中清楚地看到这一点:
/* {{{ proto array array_keys(array input [, mixed search_value[, bool strict]])
Return just the keys from the input array, optionally only for the specified search_value */
PHP_FUNCTION(array_keys)
{
zval *input, /* Input array */
*search_value = NULL, /* Value to search for */
**entry, /* An entry in the input array */
res, /* Result of comparison */
*new_val; /* New value */
int add_key; /* Flag to indicate whether a key should be added */
zend_bool strict = 0; /* do strict comparison */
HashPosition pos;
int (*is_equal_func)(zval *, zval *, zval * TSRMLS_DC) = is_equal_function;
if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "a|zb", &input, &search_value, &strict) == FAILURE) {
return;
}
if (strict) {
is_equal_func = is_identical_function;
}
/* Initialize return array */
if (search_value != NULL) {
array_init(return_value);
} else {
array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(input)));
}
add_key = 1;
/* Go through input array and add keys to the return array */
zend_hash_internal_pointer_reset_ex(Z_ARRVAL_P(input), &pos);
while (zend_hash_get_current_data_ex(Z_ARRVAL_P(input), (void **)&entry, &pos) == SUCCESS) {
if (search_value != NULL) {
is_equal_func(&res, search_value, *entry TSRMLS_CC);
add_key = zval_is_true(&res);
}
if (add_key) {
MAKE_STD_ZVAL(new_val);
zend_hash_get_current_key_zval_ex(Z_ARRVAL_P(input), new_val, &pos);
zend_hash_next_index_insert(Z_ARRVAL_P(return_value), &new_val, sizeof(zval *), NULL);
}
zend_hash_move_forward_ex(Z_ARRVAL_P(input), &pos);
}
}
/* }}} */
附注: