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Recently, we often have to match and replace strings. In the past, we usually used str_replace or preg_replace. It is said that strtr is very efficient, so we compare it with each other:

The code is as follows:

$I = 0

$t = microtime (true)

For (; $iPrecious, 'bounded = >' d'.

For (I = 0; I)

< trlen; i++) { xlat[(unsigned char) str_from[i]] = str_to[i]; } //替换(不过觉得这个函数的效率还有可以改进的地方，因为如果需要替换的字符只是占整个字符串很少的部分，这样就有大部分的赋值操作其实并没有什么意义，这样的情况下感觉先判断再赋值感觉会高效一点。有空测试一下) for (i = 0; i < len; i++) { str[i] = xlat[(unsigned char) str[i]]; } return str; } 可见，在处理strtr('abcdaaabcd', 'ab', 'efd')这样的操作时，应该是很高效的。 （注意：这个操作输出efcdeeefcd） 再看看php_strtr_array： 复制代码 代码如下: static void php_strtr_array(zval *return_value, char *str, int slen, HashTable *hash) { zval **entry; char *string_key; uint string_key_len; zval **trans; zval ctmp; ulong num_key; int minlen = 128*1024; int maxlen = 0, pos, len, found; char *key; HashPosition hpos; smart_str result = {0}; HashTable tmp_hash; //把替换数组从hash复制到tmp_hash,并记录下标字符串的最大和最小长度 zend_hash_init(&tmp_hash, 0, NULL, NULL, 0); zend_hash_internal_pointer_reset_ex(hash, &hpos); while (zend_hash_get_current_data_ex(hash, (void **)&entry, &hpos) == SUCCESS) { switch (zend_hash_get_current_key_ex(hash, &string_key, &string_key_len, &num_key, 0, &hpos)) { case HASH_KEY_IS_STRING: len = string_key_len-1; if (len < 1) { zend_hash_destroy(&tmp_hash); RETURN_FALSE; } zend_hash_add(&tmp_hash, string_key, string_key_len, entry, sizeof(zval*), NULL); if (len >

Maxlen) {

Maxlen = len

}

If (len

< minlen) { minlen = len; } break; //下标如果是整形的话会转换成字符串类型，例如：array(10=>

Convert 'aa') to array (' 10 percent = > 'aa')

Case HASH_KEY_IS_LONG:

Z_TYPE (ctmp) = IS_LONG

Z_LVAL (ctmp) = num_key

Convert_to_string & ctmp)

Len = Z_STRLEN (ctmp)

Zend_hash_add (& tmp_hash, Z_STRVAL (ctmp), len+1, entry, sizeof (zval*), NULL)

Zval_dtor & ctmp)

If (len > maxlen) {

Maxlen = len

}

If (len

< minlen) { minlen = len; } break; } zend_hash_move_forward_ex(hash, &hpos); } key = emalloc(maxlen+1); pos = 0; //从字符串的第一个字符开始循环匹配，pos记录当前查找的位置 while (pos < slen) { //当前位置加上最大长度，如果大于字符串长度，则最大长度就需要改变 if ((pos + maxlen) >

Slen) {

Maxlen = slen-pos

}

Found = 0

Memcpy (key, str+pos, maxlen)

/ / match from the maximum length, that is to say, for 'abcd',', if ab is replaced by f instead of a with e first, it will be replaced by an if it is array ('a'= >'e').

For (len = maxlen; len > = minlen; len--) {

Key [len] = 0

/ / because the hash table is used, the efficiency is quite high.

If (zend_hash_find (& tmp_hash, key, len+1, (void**) & trans) = = SUCCESS) {

Char * tval

Int tlen

Zval tmp

If (Z_TYPE_PP (trans)! = IS_STRING) {

Tmp = * * trans

Zval_copy_ctor & tmp)

Convert_to_string & tmp)

Tval = Z_STRVAL (tmp)

Tlen = Z_STRLEN (tmp)

} else {

Tval = Z_STRVAL_PP (trans)

Tlen = Z_STRLEN_PP (trans)

}

/ / join result

Smart_str_appendl (& result, tval, tlen)

/ / jump forward

Pos + = len

Found = 1

If (Z_TYPE_PP (trans)! = IS_STRING) {

Zval_dtor & tmp)

}

Break

}

}

If (! Found) {

Smart_str_appendc (& result, str [pos++])

}

}

Efree (key)

Zend_hash_destroy & tmp_hash)

Smart_str_0 & result)

RETVAL_STRINGL (result.c, result.len, 0)

}

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