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PHP Function to Validate Bank Routing Numbers

Posted on 03/16/2010 at 04:10 pm by Kevin Wentworth
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I needed to validate that a Bank Routing Number was valid, much like the algorithms out there to check if a Credit Card number is valid. I did a little searching and didn't find a PHP function that would do the trick. I decided to write my own, based on this javascript function, and publish it for anyone who wants to use it:

Function to Validate Bank Routing Numbers:

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function checkRoutingNumber($routingNumber = 0) {
    $routingNumber = preg_replace('[\D]', '', $routingNumber); //only digits
    if(strlen($routingNumber) != 9) {
        return false;   
    }
                
    $checkSum = 0;
    for ($i = 0, $j = strlen($routingNumber); $i < $j; $i+= 3 ) {
        //loop through routingNumber character by character
        $checkSum += ($routingNumber[$i] * 3);
        $checkSum += ($routingNumber[$i+1] * 7);
        $checkSum += ($routingNumber[$i+2]);
    }
                
    if($checkSum != 0 and ($checkSum % 10) == 0) {
        return true;
    } else { 
        return false;
    }
}

Cheers,
-Kevin Wentworth

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Php | Web Programming | Example

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PHP Function to Validate Bank Routing Numbers

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