<?php
$string = '<p align="center"><font face="Proxima Nova Alt Th" size="21" color="#ffffff" letterSpacing="-1.000000" kerning="1"><b>YOUR</b></font></p><p align="center"><font face="Proxima Nova Alt Th" size="21" color="#ffffff" letterSpacing="-1.000000" kerning="1"><b>OFFER</b></font></p>';
$regex = "/font face=\"([a-z 0-9]+)\"/i";
$font = preg_replace_callback($regex, function($matches) {
return $matches[1]; // I WANT TO GET THE FONT HERE, Y U NO WORK (try var dumping matches and you'll see $matches[1] is what I want)
}, $string);
echo $font;
<p align="center"><Proxima Nova Alt Th size="21" color="#ffffff" letterSpacing="-1.000000" kerning="1"><b>YOUR</b></font></p><p align="center"><Proxima Nova Alt Th size="21" color="#ffffff" letterSpacing="-1.000000" kerning="1"><b>OFFER</b></font></p>