PHP 函数：strcmp,strncmp,strstr,strpos
由 yourfar 于 周六, 04/05/2008 - 13:32 提交。
strcmp,strncmp,strstr,strpos
strcmp:
$mystring = 'abc';
$findme = 'a';
$pos = strpos($mystring, $findme);
区分大小写的字符串比较.
int strcasecmp ( string str1, string str2 )
如果str1小于str2则返回0, 两个字符串相等时返回0.
eg:
CODE:
$email = 'user@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com
?>
$domain = strstr($email, '@');
echo $domain; // prints @example.com
?>
strcasecmp用法一致,但不区分大小写.
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strncmp
和strcmp的区别在于,可以限制他只比较前面的n个字符.
int strncmp ( string str1, string str2, int len )
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strstr
string strstr ( string haystack, string needle )
手册上是这样写的strstr -- Find first occurrence of a string .找到第一次出现的位置.区分大小写
但是从手册中给出的例子和注意事项看,他被用来提取出string needle后边的字符串
eg:
CODE:
$email = 'user@example.com';
$domain = strstr($email, '@');
echo $domain; // prints @example.com
?>
$domain = strstr($email, '@');
echo $domain; // prints @example.com
?>
不想区分大小写就用stristr,
只想确定string needle是否出现在haystack中或者只要提供出现位置时,使用strpos更省资源.
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strpos
Find position of first occurrence of a string
返回目标字符在字符串中第一次出现的位置.如果找不到则返回布尔值false.区分大小写
注意:判断是否出现时应使用"===",因为该函数可能返回"0"即第一个字符就是要找的.
eq:
CODE:
$mystring = 'abc';
$findme = 'a';
$pos = strpos($mystring, $findme);
// Note our use of ===. Simply == would not work as expected
// because the position of 'a' was the 0th (first) character.
if ($pos === false) {
echo "The string '$findme' was not found in the string '$mystring'";
} else {
echo "The string '$findme' was found in the string '$mystring'";
echo " and exists at position $pos";
}
// We can search for the character, 忽略 offset 位置前的字符串
$newstring = 'abcdef abcdef';
$pos = strpos($newstring, 'a', 1); // $pos = 7, not 0
?>
offset:指出开始搜索的位置,不论offset是几,返回的位置都是从字符串开头算起的.
不想区分大小写用stripos
找最后一次出现位置用strrpos
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