Home > MySQL > Frequently Used PHP Functionsprinter version

MySQL Frequently Used Functions

The PHP MySQL library functions covered in the previous tutorials are probably enough to build a simple web application.

Below are some additional functions that are frequently used in web applications.

The mysql_num_rows() Function

This function can be used after a SELECT query to find the number of rows that the query returned.

It takes only one argument - the result set returned from the previous SELECT query and returns the number of rows.

Example of a Row Count after a Select Query

<?php
$query = "SELECT * FROM people";
$result = mysql_query($query, $connection) or exit(mysql_error());
$num_rows = mysql_num_rows($result);
echo($num_rows);
?>

Note: If you only require the number of rows in a table and not the contents then the code above is inefficient. Instead you should use SELECT COUNT(*) as shown below.

Finding the Row Count using SELECT COUNT(*)

<?php
$query = "SELECT COUNT(*) FROM people";
$result = mysql_query($query, $connection) or exit(mysql_error());
$row = mysql_fetch_array($result);
$num_rows = $row[0];
echo($num_rows);
?>

The mysql_num_fields() Function

This function can be used after a SELECT query to find the number of attributes in a row that the query returned.

It takes only one argument - the result set returned from the previous SELECT query and returns the number of attributes.

Example of an Attribute Count after a Select Query

<?php
$query = "SELECT * FROM people";
$result = mysql_query($query, $connection) or exit(mysql_error());
$num_fields = mysql_num_fields($result);
echo($num_fields);
?>

The mysql_data_seek() Function

This function is used to return a result that starts at a row other than the first row. The function is run after the SELECT query but before fetching a row.

It requires two arguments, the result set from SELECT query and the offset from the first row.

Example of mysql_data_seek()

<?php
$query = "SELECT * FROM people";
$result = mysql_query($query, $connection) or exit(mysql_error());
mysql_data_seek($result, 2);
$row = mysql_fetch_array($result);
$lastname = $row["lastname"];
echo($lastname);
?>

The mysql_close() Function

This function is used to close a connection opened with mysql_connect() and takes as an argument the connection handle returned by that function.

If no argument is supplied it assumes the most recently opened connection.

You're unlikely to use this function since connections are closed automatically when a PHP script terminates.

Basics Creating a Document Head and Body Elements Formatting Text Creating Lists Embedding Images URLs Explained Linking to Documents Creating Tables Forms Form Basics Input and Textarea Select Lists Frames Framesets The Frame Element Nested Framesets Targetting Frames Inline Frames		Tips and Tricks Meta Tags Transition Effects HTML Generators Create a Document Create a List Create a Table

Basics Implementing CSS CSS Syntax Pseudo Classes/Elements CSS Classes CSS Properties Font Properties Color and Background Text Properties Border Properties Margins and Padding Size and Position		Tips and Tricks Menu Buttons Special Effects

Basics Running a Script Variables Expressions and Operators Objects.Properties.Methods The Date Object Strings Regular Expressions Defining RegExp Patterns Branches and Conditions Loops Arrays Array Basics Array Methods Sorting Arrays User-Defined Functions Cookies Windows Frames		Tips and Tricks Image Replacement Using Includes Form Validation Debugging

Basics Creating a Script Running a Script Variables Expressions and Operators Strings Strings Basics Strings and Substrings Replacing Substrings Regular Expressions Branches and Conditions Loops Arrays Array Basics Array Functions Sorting Arrays User-Defined Functions Include and Require Uploading Files File Functions Session Variables		Tips and Tricks Page Templates Form Reply Scripts Form Validation JavaScript to PHP