$re = '/\\\\"(.*?)\\\\"/';
$str = '{"unit":{"id":1,"val":"px","name":"px"},"type":{"id":3,"val":"HORIZONTAL_BAR","name":"Horizontal Bar"},"zoom":{"id":2,"val":"DEFAULT","name":"Show"},"scale":{"id":2,"val":"TRUE","name":"Show"},"fullscreen":{"id":1,"val":"FALSE","name":"Hide"},"street":{"id":2,"val":"TRUE","name":"Show"},"poi":{"id":1,"val":"FALSE","name":"Disable"},"draggable":{"id":2,"val":"TRUE","name":"Enable"},"doubleclick":{"id":2,"val":"TRUE","name":"Enable"},"mouse":{"id":2,"val":"TRUE","name":"Enable"},"gesture":{"id":2,"val":"auto","name":"Auto"},"map":{"id":1,"val":"ROADMAP","name":"Road Map"},"mapid":"mapkit-9479","api":"","lat":"51.343695608206275","lng":"-2.4871419408111706","zoomlvl":13,"width":600,"height":400,"position":{},"route":{},"infowindow":{"enable":false,"title":false,"tel":false,"email":false,"web":false,"desc":false},"visible":1,"lon":"-2.4871419408111706","user_id":4575,"map_url":"26T9Te","snazzy":{"id":12,"snazzy_id":11,"name":"Blue","json":"[{\\"featureType\\":\\"all\\",\\"stylers\\":[{\\"hue\\":\\"#0000b0\\"},{\\"invert_lightness\\":"true"},{\\"saturation\\":-30}]}]"}}';
$subst = "\"$1\"";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php