<?php

$text = '<p width="50px;" style="padding:0px;"><strong style="padding:0;margin:0;">hello</strong></p><table style="text-align:center"></table>';

/* temporary change table tags */
$textTemp = str_replace(array("<table","/table>"),array('###','+++'),$text);


$text_2 = preg_replace("/<([a-z][a-z0-9]*)[^>]*?(\/?)>/i",'<$1$2>', $textTemp);



echo "\n\n";
$finalText =  str_replace(array("###","+++"),array("<table","/table>"),$text_2);
echo $finalText ;

?>

<p><strong>hello</strong></p><table style="text-align:center"></table>