What are the recommended PHP functions or methods for converting date formats to match SQL date fields?

When working with dates in PHP and SQL, it's important to ensure that the date formats match to avoid any issues when inserting or retrieving data from a database. To convert date formats to match SQL date fields, you can use the `date()` function in PHP to format the date string accordingly. Additionally, you can use the `strtotime()` function to convert a date string into a Unix timestamp, which can then be formatted using `date()`.

// Example of converting date format to match SQL date field
$dateString = "2022-12-31";
$sqlDateFormat = date("Y-m-d", strtotime($dateString));
echo $sqlDateFormat; // Output: 2022-12-31