<?php
 
$regexpNumber = '/^((\\s*\+\\s*7)|\\s*8)([^a-zA-Z0-9]*[0-9]){10}\b$/';
$regexpSymbol = ['/(\\s*\+\\s*7\\s*)/', '/(\\D*)/'];
 
$numbers = ['+74951234567', '8-495-1-234-567', 
  ' 8 (8122) 56-56-56', '8-911-1234567', '84951a234567', '8495123456a', 
  '+1 234 5678901',];
 
$correctNumbers = array();
 
foreach($numbers as $number) {
	if(preg_match($regexpNumber, $number)) {
		$correctNumbers[] = preg_replace($regexpSymbol, ['8', ''], $number);
	}
}
 
echo var_dump($correctNumbers);

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