What are the built-in functions of PHP?

PHP provides a series of built-in functions for processing strings, dates, errors, and mathematical calculations. These functions include (but are not limited to): String handling (strlen, strtoupper, strpos, substr) Date handling (date, strtotime, strftime) Error handling (trigger_error, set_error_handler) Mathematical functions (abs, round, pow, sqrt, rand) These functions can be implemented through practical cases, such as using built-in functions to generate random passwords.

Built-in Functions of PHP Functions

PHP provides a series of built-in functions that are predefined for a variety of common tasks the behavior of. These functions range from string processing to date processing to error handling.

String processing function

• strlen(): Returns the length of the string
• strtoupper (): Convert the string to uppercase
• strtolower(): Convert the string to lowercase
• strpos(): Find the position of a substring in a string
• substr(): Extract a substring from a string

Date processing function

• date(): Returns the current date and time
• strtotime(): Converts a date and time string to a time Stamp
• mktime(): Create a date and time based on the given timestamp
• strftime(): Format the date according to the given format and time

Error handling function

• trigger_error(): Trigger custom error message
• set_error_handler(): Set a custom error handler
• restore_error_handler(): Restore the default error handler

Mathematics Function

• abs(): Returns the absolute value
• round(): Rounds the number
• pow(): Calculate the power
• sqrt(): Calculate the square root
• rand(): Generate Random numbers

Practical case

Consider the following code, which uses PHP built-in functions to generate random passwords:

<?php
$length = 10; // 密码长度
$charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'; // 字符集

function generatePassword($length, $charset) {
  $password = '';
  for ($i = 0; $i < $length; $i++) {
    $randIndex = rand(0, strlen($charset) - 1);
    $password .= substr($charset, $randIndex, 1);
  }
  return $password;
}

$password = generatePassword($length, $charset);
echo "生成的密码：$password";
?>

Output ：

生成的密码：Z2sIxXns0w

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