Why is call to undefined function mysql_query() appearing? - Troubleshooting Guide

As a developer, you may have encountered the error message "call to undefined function mysql_query()" while working on a PHP project. This error occurs when you try to use the deprecated mysql_query() function in your code. In this guide, we will explain the reasons for this error and provide step-by-step solutions to fix it.

What is the mysql_query() function?

mysql_query() is a PHP function used to execute a MySQL query. It was a widely used function in PHP applications until PHP version 7.0, which marked it as deprecated. Deprecated functions are no longer recommended for use and can cause compatibility issues in newer versions of PHP.

Why is the "call to undefined function mysql_query()" error appearing?

The "call to undefined function mysql_query()" error appears because the mysql_query() function is no longer available in PHP 7.0 and above. If your code uses this function, you will encounter this error when running it on a PHP 7.0 or later version.

Solution: Replace mysql_query() function with mysqli_query() function

To fix this error, you need to replace the mysql_query() function with the mysqli_query() function, which is the recommended alternative for executing MySQL queries in PHP 7.0 and above.

Here are the steps to replace mysql_query() with mysqli_query():

  1. Find all instances of mysql_query() in your code.
  2. Replace mysql_query() with mysqli_query().
  3. Change the connection parameter from mysql_connect() to mysqli_connect().
  4. Update any queries that use the mysql_ prefix to use the mysqli_ prefix.

Here is an example of how to use the mysqli_query() function:

$conn = mysqli_connect("localhost", "username", "password", "database");
$sql = "SELECT * FROM users";
$result = mysqli_query($conn, $sql);


Q: Can I still use mysql_query() function in PHP 7.0 and above?

A: No, the mysql_query() function has been deprecated in PHP 7.0 and above and is no longer recommended for use.

Q: What is the difference between mysql_query() and mysqli_query()?

A: mysql_query() is a deprecated function that was used to execute MySQL queries in PHP applications. mysqli_query() is the recommended alternative function for executing MySQL queries in PHP 7.0 and above.

Q: How do I change the connection parameter from mysql_connect() to mysqli_connect()?

A: Replace mysql_connect() with mysqli_connect() and update the connection parameters accordingly.

Q: What happens if I don't replace mysql_query() with mysqli_query()?

A: If you don't replace mysql_query() with mysqli_query(), your code will encounter the "call to undefined function mysql_query()" error when running on PHP 7.0 and above.

Q: Are there any other deprecated functions that I should replace in my code?

A: Yes, there are several other deprecated functions in PHP 7.0 and above that you should replace in your code. Some examples include mysql_connect(), mysql_select_db(), and ereg(). You can find a full list of deprecated functions on the PHP website.

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