How to determine if a PHP function is compatible across versions?

Use PHP's function compatibility tool or consult the compatibility table to determine the compatibility of PHP functions across versions: the function compatibility tool is used to check the compatibility of specific functions in different PHP versions. The compatibility table provides a list of each function's status in different PHP versions, including available, deprecated, and removed.

How to determine whether a PHP function is compatible across versions?

When you use external libraries or extensions in your PHP project, you need to ensure that your code runs properly under different PHP versions. However, as PHP versions are constantly updated, some functions may be deprecated or removed, which may cause problems with your code.

To solve this problem, you can use PHP's Function Compatibility tool. This tool allows you to check the compatibility of specific functions in different PHP versions.

Practical case

Let us take the mysql_connect() function as an example. This function is used to connect to a MySQL database, but is deprecated in PHP 7.0 and mysqli_connect() is recommended instead. Let's check the compatibility of this function in different PHP versions using the Function Compatibility tool:

php -rf
php > phpinfo(INFO_COMPATIBILITY);

The output looks like:

mysql_connect()                indicates function is present in versions < 7.0 and deprecated in versions >= 7.0

This output tells us The mysql_connect() function was available before PHP 7.0, but has been deprecated in PHP 7.0 and later.

Using the compatibility table

You can also consult the compatibility table in the PHP documentation. This table provides a list of the status of each function under different PHP versions:

• Available: The function is available in this PHP version.
• Deprecated: This function is deprecated in this version of PHP, but can still be used.
• Removed: This function has been removed in this PHP version and can no longer be used.

The table can be found at the following link:

https://www.php.net/manual/en/migration70.incompatible.php

Conclusion

By using the Function Compatibility tool or consulting the compatibility matrix, you can ensure code compatibility when using external libraries and extensions across different PHP versions.

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