How are PHP functions divided according to functionality?

PHP functions are classified by function, including: string operations (str_replace, substr, etc.) numeric operations (round, abs, etc.) array operations (array_merge, array_filter, etc.) file operations (fopen, fwrite, etc.) date and time operations (date , mktime, etc.) system operations (exec, passthru, etc.)

Divide PHP functions according to their functions

The functions in PHP are divided according to their functions Functions can be divided into the following categories:

String operations

• str_replace: replace part of the string
• substr: intercept characters String
• strtoupper: Convert the string to uppercase
• strtolower: Convert the string to lowercase

Number operations

• round: Round a number
• abs: Return the absolute value of a number
• pow: Calculate the power
• sqrt: Calculate the square root

Array operations

• array_merge: Merge multiple arrays
• array_filter: Filter elements in the array that meet specific conditions
• array_map: Apply a callback function to each element in the array
• array_reduce: Use the callback function to process the elements in the array one by one and return a single value

File operations

• fopen: Open a file
• fwrite: Write data to the file
• fclose: Close a file
• file_exists: Check whether the file exists

Date and time operations

• date: Return the current date and time
• mktime: Based on the specified year, month, Create timestamp of day, hour, minute, second
• gmdate: Return Greenwich Mean Time
• date_default_timezone_set: Set the default time zone

System operation

• exec: Execute system commands
• passthru: Pass system command output to the browser
• getenv: Get environment variables
• phpinfo: Display PHP configuration information

Practical case

The following is a sample script using PHP functions:

<?php

// 字符串操作
$originalString = "Hello World";
$newString = str_replace("World", "Universe", $originalString);

// 数字操作
$number = 12.3456;
$roundedNumber = round($number, 2);

// 数组操作
$array1 = [1, 2, 3];
$array2 = [4, 5, 6];
$mergedArray = array_merge($array1, $array2);

// 文件操作
$fileName = "myfile.txt";
$file = fopen($fileName, "w");
fwrite($file, "Hello from PHP!");
fclose($file);

// 日期和时间操作
$timestamp = 1651562400;
$formattedDate = date("Y-m-d H:i:s", $timestamp);

// 系统操作
exec("echo 'Hello from command line!'");

?>

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