How to handle PHP input and output errors and generate related error prompts

How to handle PHP input and output errors and generate related error prompts

When writing PHP programs, input and output errors are one of the problems we often encounter. Correctly handling input and output errors can not only improve the reliability of the program, but also facilitate our debugging and error repair. This article will introduce some common PHP input and output error handling methods, and provide relevant error code examples.

1. Error handling related to files and directories

1. Judging whether the file exists

When performing file operations, we need to first determine whether the file exists to avoid operating on non-existent files. You can use PHP's file_exists() function to determine whether a file exists. If the file does not exist, relevant error information can be output.

Code example:

$file = 'test.txt';
if (file_exists($file)) {
    // 文件存在，进行操作
    // ...
} else {
    // 文件不存在，输出错误信息
    echo '文件不存在！';
}

2. Judge whether the file is readable/writable

When performing file reading or writing operations, it is also necessary to Determine whether the file has corresponding access permissions. You can use PHP's is_readable() and is_writable() functions to judge. If the file is not readable/writable, relevant error information can be output.

Code example:

$file = 'test.txt';
if (is_readable($file)) {
    // 文件可读，进行读取操作
    // ...
} else {
    // 文件不可读，输出错误信息
    echo '文件不可读！';
}

if (is_writable($file)) {
    // 文件可写，进行写入操作
    // ...
} else {
    // 文件不可写，输出错误信息
    echo '文件不可写！';
}

3. Judging whether the directory exists

When performing directory operations, it is also necessary to determine whether the directory exists to avoid judging whether it does not exist. directory to operate. You can use PHP's is_dir() function to determine whether the directory exists. If the directory does not exist, relevant error information can be output.

Code sample:

$dir = 'test';
if (is_dir($dir)) {
    // 目录存在，进行操作
    // ...
} else {
    // 目录不存在，输出错误信息
    echo '目录不存在！';
}

2. Database related error handling

1. Database connection error handling

When connecting to the database, if If a connection error occurs, we need to provide relevant error message. You can use PHP's mysqli_connect_error() function to obtain connection error information and output it.

Code example:

$host = 'localhost';
$user = 'root';
$password = 'password';
$database = 'test';

$conn = mysqli_connect($host, $user, $password, $database);
if (!$conn) {
    // 连接错误，输出错误信息
    echo '数据库连接错误：' . mysqli_connect_error();
}

2. Database query error handling

When performing database query operations, you also need to consider possible error conditions. You can use PHP's mysqli_error() function to obtain query error information and output it.

Code example:

$query = "SELECT * FROM users";
$result = mysqli_query($conn, $query);
if (!$result) {
    // 查询错误，输出错误信息
    echo '数据库查询错误：' . mysqli_error($conn);
}

3. Customized error handling

In addition to handling file and database-related errors, we can also customize error handling functions to facilitate other Types of errors are handled and error messages are reported. You can use PHP's set_error_handler() function to set a custom error handling function.

Code example:

function custom_error_handler($errno, $errstr, $errfile, $errline) {
    echo '自定义错误：' . $errstr . '。发生在' . $errfile . '的第' . $errline . '行。';
}

set_error_handler('custom_error_handler');

// 触发一个自定义错误
trigger_error('这是一个自定义错误。', E_USER_ERROR);

The above is the method for handling PHP input and output errors and the relevant content for generating relevant error prompts. In the actual development process, rational use of these methods can improve the reliability of the program and make it easier to debug and maintain. I hope this article can help you with error handling during PHP development.

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