PHP function collection and usage guide

PHP Function Collection and Usage Guide

Preface

PHP has a rich function library. Covers a wide range of functionality, from string processing to array operations to database interaction. Mastering these functions is crucial to writing PHP programs efficiently.この记事 will provide an outline and usage guide for PHP functions, along with practical cases.

String processing

• strlen(): Get the string length
• strtoupper(): Convert the string to uppercase
• strtolower(): Convert the string to lowercase
• substr(): Return the character Part of the string
• str_replace(): Replace specific text in the string

$str = "Hello world!"; echo "字符串长度：" . strlen($str); // 12 echo "大写字符串：" . strtoupper($str); // HELLO WORLD! echo "小写字符串：" . strtolower($str); // hello world! echo "获取子字符串：" . substr($str, 0, 5); // Hello echo "替换文本：" . str_replace("world", "everyone", $str); // Hello everyone!

Array operations

• count(): Get the length of the array
• array_push(): Add elements to the end of the array
• array_pop(): Remove elements from the end of the array
• array_merge(): Merge two arrays
• array_filter(): Filter arrays based on conditions

$arr = [1, 2, 3, 4, 5]; echo "数组长度：" . count($arr); // 5 echo "添加元素：" . array_push($arr, 6); // 6 echo "移除尾部元素：" . array_pop($arr); // 6 $arr2 = [6, 7, 8]; echo "合并数组：" . implode(", ", array_merge($arr, $arr2)); // 1, 2, 3, 4, 5, 6, 7, 8 echo "过滤数组：" . implode(", ", array_filter($arr, function($n) { return $n > 2; })); // 3, 4, 5

Database interaction

• mysqli_connect(): Connect to the database server
• mysqli_query (): Execute SQL query
• mysqli_fetch_assoc(): Get the associative array from the result set
• mysqli_close(): Close the database connection

$servername = "localhost"; $username = "root"; $password = ""; $dbname = "myDB"; // 连接到数据库 $conn = mysqli_connect($servername, $username, $password, $dbname); // 执行 SQL 查询 $result = mysqli_query($conn, "SELECT * FROM users"); // 获取查询结果 while ($row = mysqli_fetch_assoc($result)) { echo "用户名：" . $row["username"]; } // 关闭数据库连接 mysqli_close($conn);

Other common functions

• date(): Get date and time
• printf(): Formatted output
• file_get_contents(): Read content from file
• mail(): Send Email
• exec(): Execute system command

Conclusion

Mastering the PHP function library is essential for efficient Writing code is crucial. This article provides an overview of commonly used PHP functions and provides detailed practical examples. By understanding these functions and their usage, you can write powerful PHP applications quickly and easily.

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