PHP - Manual: str_starts_with

2024-11-13

str_word_count »

« str_split

str_starts_with

(PHP 8)

str_starts_with — Checks if a string starts with a given substring

说明

str_starts_with(string $haystack, string $needle): bool

Performs a case-sensitive check indicating if haystack begins with needle.

参数

haystack: The string to search in.
needle: The substring to search for in the haystack.

返回值

Returns true if haystack begins with needle, false otherwise.

范例

示例 #1 Using the empty string ''


<?php
if (str_starts_with('abc', '')) {
    echo "All strings start with the empty string";
}
?>

以上例程会输出：

All strings start with the empty string

示例 #2 Showing case-sensitivity


<?php
$string = 'The lazy fox jumped over the fence';

if (str_starts_with($string, 'The')) {
    echo "The string starts with 'The'\n";
}

if (str_starts_with($string, 'the')) {
    echo 'The string starts with "the"';
} else {
    echo '"the" was not found because the case does not match';
}

?>

以上例程会输出：

The string starts with 'The'
"the" was not found because the case does not match

注释

注意: 此函数可安全用于二进制对象。

参见

str_contains() - Determine if a string contains a given substring
str_ends_with() - Checks if a string ends with a given substring
stripos() - 查找字符串首次出现的位置（不区分大小写）
strrpos() - 计算指定字符串在目标字符串中最后一次出现的位置
strripos() - 计算指定字符串在目标字符串中最后一次出现的位置（不区分大小写）
strstr() - 查找字符串的首次出现
strpbrk() - 在字符串中查找一组字符的任何一个字符
substr() - 返回字符串的子串
preg_match() - 执行匹配正则表达式

add a note

User Contributed Notes 3 notes

down

Paul Phillips ¶

1 year ago


You can use this in PHP versions less than 8.

<?php
function str_starts_with ( $haystack, $needle ) {
  return strpos( $haystack , $needle ) === 0;
}

down

jgusta ¶

1 year ago


With credit to Paul Phillips for the original polyfill posted.

If you do not have PHP 8, you can use these functions to get the capability of the new string functions. 

But! Remember to use a conditional check to make sure the function is not already defined.

<?php
// source: Laravel Framework
// https://github.com/laravel/framework/blob/8.x/src/Illuminate/Support/Str.php
if (!function_exists('str_starts_with')) {
    function str_starts_with($haystack, $needle) {
        return (string)$needle !== '' && strncmp($haystack, $needle, strlen($needle)) === 0;
    }
}
if (!function_exists('str_ends_with')) {
    function str_ends_with($haystack, $needle) {
        return $needle !== '' && substr($haystack, -strlen($needle)) === (string)$needle;
    }
}
if (!function_exists('str_contains')) {
    function str_contains($haystack, $needle) {
        return $needle !== '' && mb_strpos($haystack, $needle) !== false;
    }
}
?>

This keeps it from breaking in case you upgrade and forget that you added it. This is a good practice generally when using the global scope for your helper functions.

down

Reinder ¶

7 months ago


In PHP7 you may want to use:

if (!function_exists('str_starts_with')) {
  function str_starts_with($str, $start) {
    return (@substr_compare($str, $start, 0, strlen($start))==0);
  }
}

AFAIK that is binary safe and doesn't need additional checks.

add a note

官方地址：https://www.php.net/manual/en/function.str-starts-with.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

str_starts_with

说明

参数

返回值

范例

注释

参见

User Contributed Notes 3 notes