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
?>