I am trying to get the preg_match '/[^0-9]/' thing below to validate or clear number only entries into a phone field. Am I on the right track as currently I cannot get it to work?

PHP Code:
public function validatePhone($phoneVal$phoneName) {
        if (
strlen($phoneVal) <= 0) {
            
$this->setError($phoneName"Phone Number Required");
        } else if (!
preg_match('/[^0-9]/''',$phoneVal)) {
            
$this->setError($phoneName"Valid Phone Number Required");
        }
    } 
PHP Code:
<p><label>Phone: <span class="required">Required</span>
          <input type="text" name="phone" class="textfield" value="<?php echo htmlentities($phone); ?>" />
          </label><span class="errors"><?php echo $phoneErr ?></span></p>

Thanks in advance for your oversight.