判断字符串是否以指定子串开头或结尾

function startsWith($str, $prefix) {return stripos($str, $prefix) === 0;
}function endsWith($str, $suffix) {return substr_compare($str, $suffix, -strlen($suffix)) === 0;
}// 示例用法
$text = "hello world";
$result = startsWith($text, "he");
echo $result;  // 输出结果: true$text = "hello world";
$result = endsWith($text, "ld");
echo $result;  // 输出结果: true

 统计字符串中指定子串出现的次数

function countSubstring($str, $substring) {return substr_count($str, $substring);
}// 示例用法
$text = "Hello, hello world!";
$result = countSubstring($text, "hello");
echo $result;  // 输出结果: 2

检查字符串是否为空或只包含空白字符

function isStringEmpty($str) {return trim($str) === "";
}// 示例用法
$text = "  ";
$result = isStringEmpty($text);
echo $result;  // 输出结果: true

格式化字符串为驼峰命名法

function toCamelCase($str) {$str = ucwords(str_replace(['-', '_'], ' ', $str));return lcfirst(str_replace(' ', '', $str));
}// 示例用法
$text = "hello-world";
$result = toCamelCase($text);
echo $result;  // 输出结果: helloWorld

检查字符串是否是回文

function isPalindrome($str) {$str = strtolower(preg_replace('/[^a-zA-Z0-9]/', '', $str));return $str === strrev($str);
}// 示例用法
$text = 'A man, a plan, a canal: Panama.';
$result = isPalindrome($text);
echo $result ? '是回文' : '不是回文';  // 输出结果: 是回文

提取字符串中的数字

function extractNumbers($str) {preg_match_all('/\d+/', $str, $matches);return implode('', $matches[0]);
}// 示例用法
$text = 'abc123def456';
$result = extractNumbers($text);
echo $result;  // 输出结果: 123456

翻转字符串中的单词顺序

function reverseWords($str) {return implode(' ', array_reverse(explode(' ', $str)));
}// 示例用法
$text = 'Hello world, this is PHP.';
$result = reverseWords($text);
echo $result;  // 输出结果: PHP. is this world, Hello

删除字符串中的空格

function removeSpaces($str) {return str_replace(' ', '', $str);
}// 示例用法
$text = 'Hello, World!';
$result = removeSpaces($text);
echo $result;  // 输出结果: Hello,World!

替换字符串中的特定内容

function replaceString($str, $search, $replace) {return str_replace($search, $replace, $str);
}// 示例用法
$text = "hello world";
$result = replaceString($text, "world", "everyone");
echo $result;  // 输出结果: hello everyone