php下使用strpos需要注意 === 运算符

<?php 
/* 
判断字符串是否存在的函数 
*/ 
function strexists($haystack, $needle) { 
return !(strpos($haystack, $needle) === FALSE);//注意这里的"===" 
} 
/* 
Test 
*/ 
$mystring = 'abc'; 
$findme = 'a'; 
$pos = strpos($mystring, $findme); // Note our use of ===. Simply == would not work as expected 
// because the position of 'a' was the 0th (first) character. 
// 简单的使用 "==" 号是不会起作用的，需要使用 "==="，因为 a 第一次出现的位置为 0 
if ($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, ignoring anything before the offset 
// 在搜索字符的时候可以使用参数 offset 来指定偏移量 
$newstring　= 'abcdef abcdef'; 
$pos　= strpos($newstring, 'a', 1); // $pos = 7, not 0 
?>