How can PHP be used to remove specific characters or symbols from a string before validation?

When validating user input in PHP, it may be necessary to remove specific characters or symbols from a string before proceeding with the validation process. This can be achieved using PHP's `str_replace()` function to replace the unwanted characters with an empty string. By doing this, you can ensure that the input contains only the desired characters for validation.

// Input string with unwanted characters
$input = "abc123!@#";

// Define an array of unwanted characters
$unwanted_chars = array("!", "@", "#");

// Remove unwanted characters from the input string
$clean_input = str_replace($unwanted_chars, "", $input);

// Validate the cleaned input
if (/* validation logic */) {
    // Proceed with further processing
} else {
    // Handle validation error
}