在哪里可以找到用于编写每个PHP“内置” PHP的算法？功能？

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我最近构建了一个基于PHP的应用程序，通常需要几（> 10）秒才能解析目标字符串（> 10秒，因为对一个典型的100kB +字符串有成千上万的检查）。我正在寻找减少执行时间的方法。

I recently built a PHP-based application that typically requires several (>10) seconds to parse a target string (>10 seconds because there are many thousands of checks on a typically 100kB+ string). I am looking for ways to reduce the execution time.

我开始怀疑如何编写PHP的每个内置函数。例如，如果您转到手册（strpos（）参考php rel = nofollow noreferrer>此链接），虽然有很多信息，但是没有算法。

I started to wonder how each of PHP's "built-in" functions are written. For example, if you go to the strpos() reference in the manual (this link), there is a lot of info but not the algorithm.

谁知道，也许我可以为我的特定应用程序编写一个比内置函数更快的函数？但是我没有办法知道例如strpos（）。该算法是否使用这种方法：

Who knows, maybe I can write a function that is faster than the built-in function for my particular application? But I have no way of knowing the algorithm for e.g. strpos(). Does the algorithm use a method such as this one:

function strposHypothetical($haystack, $needle) { $haystackLength = strlen($haystack); $needleLength = strlen($needle);//for this question let's assume > 0 $pos = false; for($i = 0; $i < $haystackLength; $i++) { for($j = 0; $j < $needleLength; $j++) { $thisSum = $i + $j; if (($thisSum > $haystackLength) || ($needle[$j] !== $haystack[$thisSum])) break; } if ($j === $needleLength) { $pos = $i; break; } } return $pos; }

还是会使用慢得多的方法，比如说substr_count（ ），如果出现的是针头，如果出现的次数> 0，则是for循环，还是其他方法？

or would it use a much slower method, with let's say combination of substr_count() for occurrences of the needle, and if occurrences > 0, then a for loop, or some other method?

我已经在应用程序中对函数和方法进行了概述，以这种方式取得重大进展。另外，请注意，此帖子并没有太大帮助。在哪里可以找到PHP中每个内置函数使用的算法，或者此信息是专有的？

I have profiled the functions and methods in my application and made significant progress in this way. Also, note that this post doesn't really help much. Where can I find out the algorithm used for each built-in function in PHP, or is this information proprietary?

推荐答案

内置-in PHP函数可在PHP源代码的 / ext / standard /中找到代码。

The built-in PHP functions can be found in /ext/standard/ in the PHP source code.

对于 strpos ，您可以在 / ext / standard / string.c 。实际上，此函数实际上使用 php_memnstr ，实际上是 zend_memnstr ：

In the case of strpos, you can find the PHP implementation in /ext/standard/string.c. At its core, this function actually uses php_memnstr, which is actually an alias of zend_memnstr:

found = (char*)php_memnstr(ZSTR_VAL(haystack) + offset, Z_STRVAL_P(needle), Z_STRLEN_P(needle), ZSTR_VAL(haystack) + ZSTR_LEN(haystack));

如果我们阅读 zend_memnstr ，我们可以找到算法本身实施 strpos ：

while (p <= end) { if ((p = (const char *)memchr(p, *needle, (end-p+1))) && ne == p[needle_len-1]) { if (!memcmp(needle, p, needle_len-1)) { return p; } } if (p == NULL) { return NULL; } p++; }

ne needle 和 p 的最后一个字符是一个指针，该指针递增以扫描 haystack 。

ne here represents the last character of needle, and p is a pointer which is incremented to scan through the haystack.

函数 memchr 是一个C函数，应该执行简单的线性运算搜索字节序列，以查找给定字节/字符在字节字符串中的首次出现。 memcmp 是一个C函数，它通过逐字节比较两个可以在字符串中的字节/字符范围来进行比较。

The function memchr is a C function which should do a simple linear search through a sequence of bytes to find the first occurrence of a given byte / character in a string of bytes. memcmp is a C function which compares two byte / character ranges which can be within strings by comparing them byte-by-byte.

此函数的伪代码版本如下：

A pseudo-code version of this function is as follows:

while (p <= end) { find the next occurrence of the first character of needle; if (occurrence is found) { set `p` to point to this new location in the string; if ((character at `p` + `length of needle`) == last character of needle) { if ((next `length of needle` characters after `p`) == needle) { return p; // Found position `p` of needle in haystack! } } } else { return NULL; // Needle does not exist in haystack. } p++; }

这是一种相当有效的算法，用于查找字符串中子字符串的索引。它与您的 strposHypothetical 几乎相同，并且在复杂度方面应同样有效，除非 memcpy 做到一旦看到字符串相差一个字符，就不会提早返回，并且当然，如果使用C语言实现，它将更精简，更快。

This is a fairly efficient algorithm for finding the index of a substring in a string. It is pretty much the same algorithm to your strposHypothetical, and should be just as efficient complexity-wise, unless memcpy doesn't return early as soon as it sees the strings differ by one character, and of course, being implemented in C, it will be leaner and faster.