In-depth analysis of strpos function in PHP

This article to share the content is about PHP strpos function in-depth analysis, the content is very detailed, the need for friends can refer to, hope can help you.

Overview

In PHP strpos , it is often used to determine whether a string exists in another string, and this article describes the strpos function and its implementation.

Strpos applications

<?php/* Strpos example *///testecho ' match: ', Strpos (' xasfsdfbk ', ' XASFSDFBK ')!== false? ' True ': ' false ', '; ', Php_eol;echo ' match: ', Strpos (' xasfsdfbk ', ' FBK ')!== false? ' True ': ' false ', '; ', Php_eol;echo ' match: ', Strpos (' xasfsdfbk ', ' xs ')! = False? ' True ': ' false ', '; ', Php_eol;echo ' match: ', Strpos (' xasfsdfbk ', ' SFS ')!== false? ' True ': ' false ', '; ', php_eol;//codestrpos (' xasfsdfbk ', ' SFS ');

Warning: The strpos function may return a Boolean value FALSE , but it may also return FALSE an equivalent non-boolean value. Please read the Boolean type section for more information. You should use === an operator to test the return value of this function.

Strpos Series functions

functions	description	version
Strpos	where to find the first occurrence of a string	PHP 4, PHP 5, PHP 7
stripos	Find where strings first appear (case-insensitive)	PHP 5, PHP 7
Strrpos	calculates the location of the last occurrence of the specified string in the target string	php 4, PHP 5, PHP 7
Strripos	calculates the last occurrence of the specified string in the target string (case-insensitive)	PHP 5, PHP 7
mb_strpos	Find where the string first appears in another string	php 4 >= 4.0.6, PHP 5, PHP 7
strstr	Find the first occurrence of a string	php 4, PHP 5, PHP 7
stristr	strstr () function ignore case version	PHP 4, PHP 5, PHP 7
Substr_count	counts the number of occurrences of a string	php 4, PHP 5, PHP 7

mb* related functions are also available, such as Mb_strpos, which performs a multi-byte secure Strpos () operation based on the number of characters.

PHP (strpos) source code

Strpos (EXT/STANDARD/STRING.C)

• PHP Source Address

Php_function (strpos) {zval *needle;    Zend_string *haystack;    char *found = NULL;    Char needle_char[2]; Zend_long offset = 0; #ifndef fast_zpp if (Zend_parse_parameters (Zend_num_args (), "Sz|l", &haystack, &needle, &    Amp;offset) = = FAILURE) {return; } #else Zend_parse_parameters_start (2, 3) z_param_str (haystack) z_param_zval (needle) z_param_option AL Z_param_long (offset) zend_parse_parameters_end (); #endif if (offset < 0) {offset + = (Zend_long) Z    Str_len (haystack); } if (Offset < 0 | | |        (size_t) offset > Zstr_len (haystack)) {php_error_docref (NULL, e_warning, "offset not contained in string");    Return_false; } if (z_type_p (needle) = = is_string) {if (!            Z_strlen_p (needle)) {Php_error_docref (NULL, e_warning, "Empty needle");        Return_false;   } found = (char*) php_memnstr (Zstr_val (haystack) + offset, z_strval_p (needle),                         Z_strlen_p (needle), Zstr_val (haystack) + Zstr_len (haystack));        } else {if (Php_needle_char (needle, needle_char)! = SUCCESS) {return_false;        } needle_char[1] = 0;                            Found = (char*) php_memnstr (Zstr_val (haystack) + offset, Needle_char,    1, Zstr_val (haystack) + Zstr_len (haystack));    } if (found) {Return_long (Found-zstr_val (haystack));    } else {return_false; }}

Php_memnstr (Main/php.h)

• PHP Source Address

#define PHP_MEMNSTR ZEND_MEMNSTR/* 338 line*/

Zend_memnstr (ZEND/ZEND_OPERATORS.H)

• PHP Source Address

/* * This function is to find needle in haystack, if there is no return null, if present, returns a pointer to needle header character in haystack */zend_memnstr (const char *haystack, const    Char *needle, size_t needle_len, const char *end) {const char *p = haystack;    const char NE = needle[needle_len-1];    ptrdiff_t off_p;    size_t off_s;    if (Needle_len = = 1) {return (const char *) MEMCHR (P, *needle, (end-p));    } off_p = End-haystack; off_s = (off_p > 0)?    (size_t) off_p:0;    if (Needle_len > off_s) {return NULL;        } if (Expected (off_s < 1024x768 | | Needle_len < 3)) {//First optimization, find only end-needle_len times end-= Needle_len; while (P <= end) {///second optimization, first determine whether the beginning and end of the string are the same again to determine the entire string if (p = (const char *) MEMCHR (p, *nee                    Dle, (end-p+1))) && ne = = p[needle_len-1]) {if (!memcmp (needle, p, needle_len-1)) {                return p;            }} if (p = = null) {return null;        } p++;    }    return NULL;    } else {return zend_memnstr_ex (haystack, needle, needle_len, end); }}

MEMCHR (string.h)

• Linux kernel version-source address

/* header file: #include <string.h> define function: void * MEMCHR (const void *s, char C, size_t n); function Description: MEMCHR () searches from the beginning to the first n bytes of the memory content referred to by S, until a Now the first byte with a value of C, a pointer to that byte is returned. Return value: Returns a pointer to the byte if the specified byte is found, otherwise 0 is returned. */#ifndef __have_arch_memchrvoid *MEMCHR (const void *s, int c, size_t N) {    const unsigned char *p = s;    while (n--! = 0) {            if ((unsigned char) c = = *p++) {            return (void *) (p-1);        }    }    return NULL;} Export_symbol (MEMCHR); #endif

MEMCMP (string.h)

• Linux kernel version-source address

/* String function memcmp   prototype: extern int memcmp (void *buf1, void *buf2, unsigned int count);    Function: Compare the memory area BUF1 and Buf2 before count bytes Description: When Buf1<buf2, return value <0 when buf1=buf2, return value     =0         when buf1>buf2, return value >0                                        */#ifndef __have_arch_memcmp#undef memcmp__visible int MEMCMP (const void *cs, const void *CT, size_t count) {
  const unsigned char *su1, *SU2;    int res = 0;    for (SU1 = cs, su2 = ct; 0 < count; ++su1, ++SU2, count--)        if (res = *SU1-*su2)! = 0) break            ;    return res;} Export_symbol (memcmp); #endif　

Tips

The Strpos function is case-sensitive.