PHP - Manual: strstr

2024-11-15

strtok »

« strspn

strstr

(PHP 4, PHP 5, PHP 7, PHP 8)

strstr — 查找字符串的首次出现

说明

strstr(string $haystack, mixed $needle, bool $before_needle = false): string

返回 haystack 字符串从 needle 第一次出现的位置开始到 haystack 结尾的字符串。

注意:
该函数区分大小写。如果想要不区分大小写，请使用 stristr()。

注意:
如果你仅仅想确定 needle 是否存在于 haystack 中，请使用速度更快、耗费内存更少的 strpos() 函数。

参数

haystack: 输入字符串。
needle: 如果 needle 不是一个字符串，那么它将被转化为整型并且作为字符的序号来使用。
before_needle: 若为 true，strstr() 将返回 needle 在 haystack 中的位置之前的部分。

返回值

返回字符串的一部分或者 false（如果未发现 needle）。

更新日志

版本	说明
5.3.0	新增可选的 `before_needle` 参数。
4.3.0	strstr() 成为二进制安全的。

范例

示例 #1 strstr() 范例


<?php
$email  = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // 打印 @example.com

$user = strstr($email, '@', true); // 从 PHP 5.3.0 起
echo $user; // 打印 name
?>

参见

preg_match() - 执行匹配正则表达式
stristr() - strstr 函数的忽略大小写版本
strpos() - 查找字符串首次出现的位置
strrchr() - 查找指定字符在字符串中的最后一次出现
substr() - 返回字符串的子串

add a note

User Contributed Notes 9 notes

down

laszlo dot heredy at gmail dot com ¶

8 years ago


strstr() is not a way to avoid type-checking with strpos().

If $needle is the last character in $haystack, and testing $needle as a boolean by itself would evaluate to false, then testing strstr() as a boolean will evaluate to false (because, if successful, strstr() returns the first occurrence of $needle along with the rest of $haystack).

<?php
findZero('01234');  // found a zero
findZero('43210');  // did not find a zero
findZero('0');      // did not find a zero
findZero('00');     // found a zero
findZero('000');    // found a zero
findZero('10');     // did not find a zero
findZero('100');    // found a zero

function findZero($numberString) {
    if (strstr($numberString, '0')) {
        echo 'found a zero';
    } else {
        echo 'did not find a zero';
    }
}
?>

Also, strstr() is far more memory-intensive than strpos(), especially with longer strings as your $haystack, so if you are not interested in the substring that strstr() returns, you shouldn't be using it anyway. 

There is no PHP function just to check only _if_ $needle occurs in $haystack; strpos() tells you if it _doesn't_ by returning false, but, if it does occur, it tells you _where_ it occurs as an integer, which is 0 (zero) if $needle is the first part of $haystack, which is why testing if (strpos($needle, $haystack)===false) is the only way to know for sure if $needle is not part of $haystack.

My advice is to start loving type checking immediately, and to familiarize yourself with the return value of the functions you are using.

Cheers.

down

gruessle at gmail dot com ¶

11 years ago


Been using this for years:

<?php
/**
*
* @author : Dennis T Kaplan
*
* @version : 1.0
* Date : June 17, 2007
* Function : reverse strstr()
* Purpose : Returns part of haystack string from start to the first occurrence of needle
* $haystack = 'this/that/whatever';
* $result = rstrstr($haystack, '/')
* $result == this
*
* @access public
* @param string $haystack, string $needle
* @return string
**/

function rstrstr($haystack,$needle)
    {
        return substr($haystack, 0,strpos($haystack, $needle));
    }
?>

You could change it to:
rstrstr ( string $haystack , mixed $needle [, int $start] )
<?php

function rstrstr($haystack,$needle, $start=0)
    {
        return substr($haystack, $start,strpos($haystack, $needle));
    }

?>

down

w3b_monk3y at yahoo dot com ¶

13 years ago


If you want to emulate strstr's new before_needle parameter pre 5.3 strtok is faster than using strpos to find the needle and cutting with substr. The amount of difference varies with string size but strtok is always faster.

down

xslidian at lidian dot info ¶

9 years ago


For those in need of the last occurrence of a string:

<?php
function strrstr($h, $n, $before = false) {
    $rpos = strrpos($h, $n);
    if($rpos === false) return false;
    if($before == false) return substr($h, $rpos);
    else return substr($h, 0, $rpos);
}
?>

down

brett dot jr dot alton at gmail dot com ¶

14 years ago


For the needle_before (first occurance) parameter when using PHP 5.x or less, try:

<?php
$haystack = 'php-homepage-20071125.png';
$needle = '-';
$result = substr($haystack, 0, strpos($haystack, $needle)); // $result = php
?>

down

Gevorg Melkumyan ¶

1 year ago


Don't  confuse this function with strtr ) I lost like 1 hour on that

down

-1

trent dot renshaw at objectst dot com dot au ¶

6 years ago


> root at mantoru dot de

PHP makes this easy for you. When working with domain portion of email addresses, simply pass the return of strstr() to substr() and start at 1:

substr(strstr($haystack, '@'), 1);

down

-20

root at mantoru dot de ¶

14 years ago


Please note that $needle is included in the return string, as shown in the example above. This ist not always desired behavior, _especially_ in the mentioned example. Use this if you want everything AFTER $needle.

<?php
function strstr_after($haystack, $needle, $case_insensitive = false) {
    $strpos = ($case_insensitive) ? 'stripos' : 'strpos';
    $pos = $strpos($haystack, $needle);
    if (is_int($pos)) {
        return substr($haystack, $pos + strlen($needle));
    }
    // Most likely false or null
    return $pos;
}

// Example
$email = 'name@example.com';
$domain = strstr_after($email, '@');
echo $domain; // prints example.com
?>

down

-26

leo dot nard at free dot fr ¶

17 years ago


When encoding ASCII strings to HTML size-limited strings, sometimes some HTML special chars were cut.


For example, when encoding "��" to a string of size 10, you would get: "à&a" => the second character is cut.


This function will remove any unterminated HTML special characters from the string...


<?php

function cut_html($string)

{

    $a=$string;


    while ($a = strstr($a, '&'))

    {

        echo "'".$a."'\n";

        $b=strstr($a, ';'); 

        if (!$b)

        {

            echo "couper...\n";

            $nb=strlen($a);

            return substr($string, 0, strlen($string)-$nb);

        }

        $a=substr($a,1,strlen($a)-1);

    }

    return $string;

}

?>

add a note

官方地址：https://www.php.net/manual/en/function.strstr.php

有任何技术问题请点击这里网站运营推广招聘

IT PHP 编程语言 Linux 开发编程科技 Elasticsearch HTML/CSS/XML 网络 JAVA NoSQL 数据库面试 C/C++ Golang Git 算法操作系统正则表达式 Redis 互联网 MySql JavaScript 运维软件国际架构设计 Mac OS TCP/IP Excel Vim Windows Socket Oracle VR MongoDB Python 运营 MemCache 商业硬件电子娱乐设计 nginx 摄影游戏 WordPress HTTP 团建数码电器

php7 安装fileinfo扩展 preg_split — 通过一个正则表达式分隔字符串 php位值,解决 PHP 中 usort 在值相同时改变原始位置的问题 [PHP] inet_pton/inet_ntop IP地址转换函数 array_multisort() 多字段排序 PHPMailer设置utf8 PHPMailer字符集CharSet ADORecordSet对象 adodb手册 PHP 8.1 [鸟哥]PHP_INT_MIN 和 -9223372036854775808 opcache预加载 Composer的Packagist资源 mysql面试题 [鸟哥]PHP FFI详解 - 一种全新的PHP扩展方式 PHP7添加redis扩展 PHP mkdir()写出来的权限与mode值不符合 Packagist / Composer 中国全量镜像 php中几种注释规范利用php soap实现web service PHP获取指定函数定义在哪个文件中及行号

略微加速

PHP官方手册 - 互联网笔记

strstr

说明

参数

返回值

更新日志

范例

参见

User Contributed Notes 9 notes