strpos() -- 找到子串第一次出现的位置

beyes

函数声明：

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

该函数从 $haystack 中查找 $needle ，如果找到则返回第一次匹配所在的位置。


测试代码：

[PHP] 纯文本查看 复制代码

<?php
$mystring = 'www.groad.net';
$findme   = 'groad';
$pos = strpos($mystring, $findme);

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";
}            
?>     

运行输出：

The string 'groad' was found in the string 'www.groad.net' and exists at position 4

上面的位置是从 0 开始算起。

函数可以指定第 3 个参数，该参数指定从第几个字符开始查找，比如：

[PHP] 纯文本查看 复制代码

<?php                                                                                                                                                                 
$mystring = 'abcdef abcdef';                                                                                                                                          
$findme   = 'a';                                                                                                                                                      
$pos = strpos($mystring, $findme, 3);                                                                                                                                 

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";
}
?>

运行输出：

The string 'a' was found in the string 'abcdef abcdef' and exists at position 7

这时候的位置是 7 。如果不指定第 3 个参数，那么第一个字符就发生了匹配，所以位置会是 0 。