Function libraries in PHP

PHP is a code language widely used in Web development. It is not only easy to use, easy to learn and understand, but also has a rich function library. These function libraries encapsulate a variety of different functions, which can improve code reusability, reduce development difficulty, and improve development efficiency during the development process. In this article, we will introduce some common function libraries and their functions in PHP for the convenience of developers.

1. String function library

The string function library in PHP provides various types of string operations, such as string splicing, interception, replacement, search, etc. The following are some common string functions:

1.strlen($str): Returns the length of the specified string.

2.str_replace("search", "replace", $str): Replace "search" in the string with "replace" and return the modified new string.

3.strpos($str, "search"): Find the position of "search" in the string and return its position.

4.strtoupper($str): Convert all characters in the string to uppercase letters.

5.substr($str, $start, $length): Starting from the specified position of the string, return a substring of the specified length.

2. Array function library

The array function library in PHP provides various array operation functions, such as array sorting, merging, querying, inserting, etc. The following are some common array functions:

1.array_push($arr, $value): Add one or more elements to the end of the array.

2.array_pop($arr): Remove and return an element from the end of the array.

3.array_merge($arr1, $arr2): Merge two arrays into a new array.

4.array_sum($arr): Returns the sum of all elements in the array.

5.in_array($elem, $arr): Determine whether the specified element is in the array. If it exists, it returns true, otherwise it returns false.

3. Date and time function library

The date and time function library in PHP provides various time operation functions, such as timestamp conversion, time formatting, date addition and subtraction, etc. The following are some common date and time functions:

1.time(): Returns the current Unix timestamp.

2.date("Y-m-d H:i:s", $timestamp): Convert timestamp to date and time in the specified format.

3.strtotime($str): Convert time in string format to Unix timestamp.

4.mktime($hour, $minute, $second, $month, $day, $year): Returns the Unix timestamp of the specified date.

5.date_add($date, date_interval_create_from_date_string("$days days")): Perform addition and subtraction operations on the specified date and return the modified new date.

4. MySQL function library

The MySQL function library in PHP provides operation functions for the MySQL database, such as connecting to the database, querying, deleting, updating, etc. The following are some common MySQL functions:

1.mysql_connect($host, $user, $password): Establish a connection with the MySQL database.

2.mysql_select_db($database): Select the database to operate.

3.mysql_query($sql): Execute the query statement and return the query results.

4.mysql_fetch_assoc($result): Convert the query results into an associative array.

5.mysql_close(): Close the connection to the MySQL database.

Summary:

The above introduces some common function libraries in PHP, including string function library, array function library, date and time function library and MySQL function library. These functions can more efficiently complete various operations required in PHP program development. Therefore, being proficient in these function libraries and being able to use these functions proficiently will achieve twice the result with half the effort in PHP program development.

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