PHP 정기 교체 FAQ: 잘못된 작업 교체 방지

// 错误示例：只会替换第一个匹配项
$text = "PHP is a popular programming language. PHP is widely used.";
$result = preg_replace("/PHP/", "JavaScript", $text);
echo $result; // 输出：JavaScript is a popular programming language. PHP is widely used.

// 正确示例：替换所有匹配项
$result = preg_replace("/PHP/g", "JavaScript", $text);
echo $result; //输出：JavaScript is a popular programming language. JavaScript is widely used.

// 保留大小写示例
$text = "PHP is a popular programming language.";
$result = preg_replace("/(PHP)/i", "<strong>$1</strong>", $text); // $1表示捕获组中匹配的内容
echo $result; //输出：<strong>PHP</strong> is a popular programming language.

// 替换特殊字符示例
$text = "This is a test with dot. This is a test with asterisk *.";
$result = preg_replace("/./", ",", $text); // 替换句号为逗号
echo $result; //输出：This is a test with dot, This is a test with asterisk *.
$result = preg_replace("/*/", "-", $text); // 替换星号为减号
echo $result; //输出：This is a test with dot. This is a test with asterisk -.

// 替换特定内容示例
$text = "Today is 2022-01-01. Tomorrow will be 2022-01-02.";
$result = preg_replace("/(d{4}-d{2}-d{2})/", "2023-01-01", $text); // 替换日期为指定日期
echo $result; //输出：Today is 2023-01-01. Tomorrow will be 2023-01-01.