FILTER_SANITIZE_NUMBER_INT constant in PHP

The FILTER_SANITIZE_NUMBER_INT constant removes all characters except digits, plus and minus signs from a string. It's commonly used to clean user input before processing numeric data.

Syntax

filter_var($value, FILTER_SANITIZE_NUMBER_INT)

Parameters

The filter_var() function with FILTER_SANITIZE_NUMBER_INT accepts −

• $value − The string to be sanitized
• FILTER_SANITIZE_NUMBER_INT − The filter constant that removes illegal characters

Return Value

Returns a string containing only digits (0-9), plus (+), and minus (-) signs. All other characters are removed.

Example

Here's how to sanitize a string containing mixed characters ?

<?php
    $var = "4-5+9p";
    $sanitized = filter_var($var, FILTER_SANITIZE_NUMBER_INT);
    var_dump($sanitized);
    
    // More examples
    $examples = ["abc123def", "++--789xyz", "12.34", "1,234"];
    
    foreach ($examples as $example) {
        echo "Original: '$example' -> Sanitized: '" . 
             filter_var($example, FILTER_SANITIZE_NUMBER_INT) . "'<br>";
    }
?>

string(5) "4-5+9"
Original: 'abc123def' -> Sanitized: '123'
Original: '++--789xyz' -> Sanitized: '++--789'
Original: '12.34' -> Sanitized: '1234'
Original: '1,234' -> Sanitized: '1234'

Key Points

• Removes all characters except digits (0-9), plus (+), and minus (-)
• Decimal points and commas are removed
• Multiple plus/minus signs are preserved
• Does not validate if the result is a valid integer

Conclusion

FILTER_SANITIZE_NUMBER_INT is useful for cleaning numeric input by removing unwanted characters while preserving essential numeric symbols. Remember to validate the sanitized result for proper integer format if needed.