$re = '/(\d\.*\d)*.+(fa-.+)\s\[&#x(.{4});\]/';
$str = ' fa-500px []
fa-adjust []
fa-adn []
fa-align-center []
fa-align-justify []
fa-align-left []
fa-align-right []
4.4 fa-amazon []
fa-ambulance []
4.6 fa-american-sign-language-interpreting []
fa-anchor []
fa-android []
4.2 fa-angellist []
fa-angle-double-down []
fa-angle-double-left []
fa-angle-double-right []
fa-angle-double-up []
fa-angle-down []
fa-angle-left []
fa-angle-right []
fa-angle-up []
fa-apple []
fa-archive []
4.2 fa-area-chart []
fa-arrow-circle-down []
fa-arrow-circle-left []
fa-arrow-circle-o-down []
4.0 fa-arrow-circle-o-left []
4.0 fa-arrow-circle-o-right []
fa-arrow-circle-o-up []
fa-arrow-circle-right []
fa-arrow-circle-up []
fa-arrow-down []
fa-arrow-left []
fa-arrow-right []
fa-arrow-up []
fa-arrows []
fa-arrows-alt []
fa-arrows-h []
fa-arrows-v []
4.6 fa-asl-interpreting (alias) []
4.6 fa-assistive-listening-systems []
fa-asterisk []
4.2 fa-at []
4.6 fa-audio-description []
4.1 fa-automobile (alias) []
fa-backward []
4.4 fa-balance-scale []
fa-ban []
4.1 fa-bank (alias) []
fa-bar-chart []
fa-bar-chart-o (alias) []
fa-barcode []
fa-bars []
4.4 fa-battery-0 (alias) []
4.4 fa-battery-1 (alias) []
4.4 fa-battery-2 (alias) []
4.4 fa-battery-3 (alias) []
4.4 fa-battery-4 (alias) []
4.4 fa-battery-empty []
4.4 fa-battery-full []
4.4 fa-battery-half []
4.4 fa-battery-quarter []
4.4 fa-battery-three-quarters []
4.3 fa-bed []
fa-beer []
4.1 fa-behance []
4.1 fa-behance-square []
fa-bell []
fa-bell-o []
4.2 fa-bell-slash []
4.2 fa-bell-slash-o []
4.2 fa-bicycle []
4.2 fa-binoculars []
4.2 fa-birthday-cake []
fa-bitbucket []
fa-bitbucket-square []
fa-bitcoin (alias) []
4.4 fa-black-tie []
4.6 fa-blind []
4.5 fa-bluetooth []
4.5 fa-bluetooth-b []
fa-bold []
fa-bolt []
4.1 fa-bomb []
fa-book []
fa-bookmark []
fa-bookmark-o []
4.6 fa-braille []
fa-briefcase []
fa-btc []
fa-bug []
4.1 fa-building []
fa-building-o []
fa-bullhorn []
fa-bullseye []
4.2 fa-bus []
4.3 fa-buysellads []
4.1 fa-cab (alias) []
4.2 fa-calculator []
fa-calendar []
4.4 fa-calendar-check-o []
4.4 fa-calendar-minus-o []
fa-calendar-o []
4.4 fa-calendar-plus-o []
4.4 fa-calendar-times-o []
fa-camera []
fa-camera-retro []
4.1 fa-car []
fa-caret-down []
fa-caret-left []
fa-caret-right []
fa-caret-square-o-down []
4.0 fa-caret-square-o-left []
fa-caret-square-o-right []
fa-caret-square-o-up []
fa-caret-up []
4.3 fa-cart-arrow-down []
4.3 fa-cart-plus []
4.2 fa-cc []
4.2 fa-cc-amex []
4.4 fa-cc-diners-club []
4.2 fa-cc-discover []
4.4 fa-cc-jcb []
4.2 fa-cc-mastercard []
4.2 fa-cc-paypal []
4.2 fa-cc-stripe []
4.2 fa-cc-visa []
fa-certificate []
fa-chain (alias) []
fa-chain-broken []
fa-check []
fa-check-circle []
fa-check-circle-o []
fa-check-square []
fa-check-square-o []
fa-chevron-circle-down []
fa-chevron-circle-left []
fa-chevron-circle-right []
fa-chevron-circle-up []
fa-chevron-down []
fa-chevron-left []
fa-chevron-right []
fa-chevron-up []
4.1 fa-child []
4.4 fa-chrome []
fa-circle []
fa-circle-o []
4.1 fa-circle-o-notch []
4.1 fa-circle-thin []
fa-clipboard []
fa-clock-o []
4.4 fa-clone []
fa-close (alias) []
fa-cloud []
fa-cloud-download []
fa-cloud-upload []
fa-cny (alias) []
fa-code []
fa-code-fork []
4.1 fa-codepen []
4.5 fa-codiepie []
fa-coffee []
fa-cog []
fa-cogs []
fa-columns []
fa-comment []
fa-comment-o []
4.4 fa-commenting []
4.4 fa-commenting-o []
fa-comments []
fa-comments-o []
fa-compass []
fa-compress []
4.3 fa-connectdevelop []
4.4 fa-contao []
fa-copy (alias) []
4.2 fa-copyright []
4.4 fa-creative-commons []
fa-credit-card []
4.5 fa-credit-card-alt []
fa-crop []
fa-crosshairs []
fa-css3 []
4.1 fa-cube []
4.1 fa-cubes []
fa-cut (alias) []
fa-cutlery []
fa-dashboard (alias) []
4.3 fa-dashcube []
4.1 fa-database []
4.6 fa-deaf []
4.6 fa-deafness (alias) []
fa-dedent (alias) []
4.1 fa-delicious []
fa-desktop []
4.1 fa-deviantart []
4.3 fa-diamond []
4.1 fa-digg []
fa-dollar (alias) []
4.0 fa-dot-circle-o []
fa-download []
fa-dribbble []
fa-dropbox []
4.1 fa-drupal []
4.5 fa-edge []
fa-edit (alias) []
fa-eject []
fa-ellipsis-h []
fa-ellipsis-v []
4.1 fa-empire []
fa-envelope []
fa-envelope-o []
4.1 fa-envelope-square []
4.6 fa-envira []
fa-eraser []
fa-eur []
fa-euro (alias) []
fa-exchange []
fa-exclamation []
fa-exclamation-circle []
fa-exclamation-triangle []
fa-expand []
4.4 fa-expeditedssl []
fa-external-link []
fa-external-link-square []
fa-eye []
fa-eye-slash []
4.2 fa-eyedropper []
4.6 fa-fa (alias) []
fa-facebook []
fa-facebook-f (alias) []
4.3 fa-facebook-official []
fa-facebook-square []
fa-fast-backward []
fa-fast-forward []
4.1 fa-fax []
fa-feed (alias) []
fa-female []
fa-fighter-jet []
fa-file []
4.1 fa-file-archive-o []
4.1 fa-file-audio-o []
4.1 fa-file-code-o []
4.1 fa-file-excel-o []
4.1 fa-file-image-o []
4.1 fa-file-movie-o (alias) []
fa-file-o []
4.1 fa-file-pdf-o []
4.1 fa-file-photo-o (alias) []
4.1 fa-file-picture-o (alias) []
4.1 fa-file-powerpoint-o []
4.1 fa-file-sound-o (alias) []
fa-file-text []
fa-file-text-o []
4.1 fa-file-video-o []
4.1 fa-file-word-o []
4.1 fa-file-zip-o (alias) []
fa-files-o []
fa-film []
fa-filter []
fa-fire []
fa-fire-extinguisher []
4.4 fa-firefox []
4.6 fa-first-order []
fa-flag []
fa-flag-checkered []
fa-flag-o []
fa-flash (alias) []
fa-flask []
fa-flickr []
fa-floppy-o []
fa-folder []
fa-folder-o []
fa-folder-open []
fa-folder-open-o []
fa-font []
4.6 fa-font-awesome []
4.4 fa-fonticons []
4.5 fa-fort-awesome []
4.3 fa-forumbee []
fa-forward []
fa-foursquare []
fa-frown-o []
4.2 fa-futbol-o []
fa-gamepad []
fa-gavel []
fa-gbp []
4.1 fa-ge (alias) []
fa-gear (alias) []
fa-gears (alias) []
4.4 fa-genderless []
4.4 fa-get-pocket []
4.4 fa-gg []
4.4 fa-gg-circle []
fa-gift []
4.1 fa-git []
4.1 fa-git-square []
fa-github []
fa-github-alt []
fa-github-square []
4.6 fa-gitlab []
fa-gittip (alias) []
fa-glass []
4.6 fa-glide []
4.6 fa-glide-g []
fa-globe []
4.1 fa-google []
fa-google-plus []
4.6 fa-google-plus-circle (alias) []
4.6 fa-google-plus-official []
fa-google-plus-square []
4.2 fa-google-wallet []
4.1 fa-graduation-cap []
fa-gratipay []
fa-group (alias) []
fa-h-square []
4.1 fa-hacker-news []
4.4 fa-hand-grab-o (alias) []
4.4 fa-hand-lizard-o []
fa-hand-o-down []
fa-hand-o-left []
fa-hand-o-right []
fa-hand-o-up []
4.4 fa-hand-paper-o []
4.4 fa-hand-peace-o []
4.4 fa-hand-pointer-o []
4.4 fa-hand-rock-o []
4.4 fa-hand-scissors-o []
4.4 fa-hand-spock-o []
4.4 fa-hand-stop-o (alias) []
4.6 fa-hard-of-hearing (alias) []
4.5 fa-hashtag []
fa-hdd-o []
4.1 fa-header []
fa-headphones []
fa-heart []
fa-heart-o []
4.3 fa-heartbeat []
4.1 fa-history []
fa-home []
fa-hospital-o []
4.3 fa-hotel (alias) []
4.4 fa-hourglass []
4.4 fa-hourglass-1 (alias) []
4.4 fa-hourglass-2 (alias) []
4.4 fa-hourglass-3 (alias) []
4.4 fa-hourglass-end []
4.4 fa-hourglass-half []
4.4 fa-hourglass-o []
4.4 fa-hourglass-start []
4.4 fa-houzz []
fa-html5 []
4.4 fa-i-cursor []
4.2 fa-ils []
fa-image (alias) []
fa-inbox []
fa-indent []
4.4 fa-industry []
fa-info []
fa-info-circle []
fa-inr []
4.6 fa-instagram []
4.1 fa-institution (alias) []
4.4 fa-internet-explorer []
4.3 fa-intersex (alias) []
4.2 fa-ioxhost []
fa-italic []
4.1 fa-joomla []
fa-jpy []
4.1 fa-jsfiddle []
fa-key []
fa-keyboard-o []
fa-krw []
4.1 fa-language []
fa-laptop []
4.2 fa-lastfm []
4.2 fa-lastfm-square []
fa-leaf []
4.3 fa-leanpub []
fa-legal (alias) []
fa-lemon-o []
fa-level-down []
fa-level-up []
4.1 fa-life-bouy (alias) []
4.1 fa-life-buoy (alias) []
4.1 fa-life-ring []
4.1 fa-life-saver (alias) []
fa-lightbulb-o []
4.2 fa-line-chart []
fa-link []
fa-linkedin []
fa-linkedin-square []
fa-linux []
fa-list []
fa-list-alt []
fa-list-ol []
fa-list-ul []
fa-location-arrow []
fa-lock []
fa-long-arrow-down []
fa-long-arrow-left []
fa-long-arrow-right []
fa-long-arrow-up []
4.6 fa-low-vision []
fa-magic []
fa-magnet []
fa-mail-forward (alias) []
fa-mail-reply (alias) []
fa-mail-reply-all (alias) []
fa-male []
4.4 fa-map []
fa-map-marker []
4.4 fa-map-o []
4.4 fa-map-pin []
4.4 fa-map-signs []
4.3 fa-mars []
4.3 fa-mars-double []
4.3 fa-mars-stroke []
4.3 fa-mars-stroke-h []
4.3 fa-mars-stroke-v []
fa-maxcdn []
4.2 fa-meanpath []
4.3 fa-medium []
fa-medkit []
fa-meh-o []
4.3 fa-mercury []
fa-microphone []
fa-microphone-slash []
fa-minus []
fa-minus-circle []
fa-minus-square []
fa-minus-square-o []
4.5 fa-mixcloud []
fa-mobile []
fa-mobile-phone (alias) []
4.5 fa-modx []
fa-money []
fa-moon-o []
4.1 fa-mortar-board (alias) []
4.3 fa-motorcycle []
4.4 fa-mouse-pointer []
fa-music []
fa-navicon (alias) []
4.3 fa-neuter []
4.2 fa-newspaper-o []
4.4 fa-object-group []
4.4 fa-object-ungroup []
4.4 fa-odnoklassniki []
4.4 fa-odnoklassniki-square []
4.4 fa-opencart []
4.1 fa-openid []
4.4 fa-opera []
4.4 fa-optin-monster []
fa-outdent []
4.0 fa-pagelines []
4.2 fa-paint-brush []
4.1 fa-paper-plane []
4.1 fa-paper-plane-o []
fa-paperclip []
4.1 fa-paragraph []
fa-paste (alias) []
fa-pause []
4.5 fa-pause-circle []
4.5 fa-pause-circle-o []
4.1 fa-paw []
4.2 fa-paypal []
fa-pencil []
fa-pencil-square []
fa-pencil-square-o []
4.5 fa-percent []
fa-phone []
fa-phone-square []
fa-photo (alias) []
fa-picture-o []
4.2 fa-pie-chart []
4.6 fa-pied-piper []
4.1 fa-pied-piper-alt []
4.1 fa-pied-piper-pp []
fa-pinterest []
4.3 fa-pinterest-p []
fa-pinterest-square []
fa-plane []
fa-play []
fa-play-circle []
fa-play-circle-o []
4.2 fa-plug []
fa-plus []
fa-plus-circle []
fa-plus-square []
4.0 fa-plus-square-o []
fa-power-off []
fa-print []
4.5 fa-product-hunt []
fa-puzzle-piece []
4.1 fa-qq []
fa-qrcode []
fa-question []
fa-question-circle []
4.6 fa-question-circle-o []
fa-quote-left []
fa-quote-right []
4.1 fa-ra (alias) []
fa-random []
4.1 fa-rebel []
4.1 fa-recycle []
4.1 fa-reddit []
4.5 fa-reddit-alien []
4.1 fa-reddit-square []
fa-refresh []
4.4 fa-registered []
fa-remove (alias) []
fa-renren []
fa-reorder (alias) []
fa-repeat []
fa-reply []
fa-reply-all []
4.1 fa-resistance (alias) []
fa-retweet []
fa-rmb (alias) []
fa-road []
fa-rocket []
fa-rotate-left (alias) []
fa-rotate-right (alias) []
4.0 fa-rouble (alias) []
fa-rss []
fa-rss-square []
4.0 fa-rub []
4.0 fa-ruble (alias) []
fa-rupee (alias) []
4.4 fa-safari []
fa-save (alias) []
fa-scissors []
4.5 fa-scribd []
fa-search []
fa-search-minus []
fa-search-plus []
4.3 fa-sellsy []
4.1 fa-send (alias) []
4.1 fa-send-o (alias) []
4.3 fa-server []
fa-share []
4.1 fa-share-alt []
4.1 fa-share-alt-square []
fa-share-square []
fa-share-square-o []
4.2 fa-shekel (alias) []
4.2 fa-sheqel (alias) []
fa-shield []
4.3 fa-ship []
4.3 fa-shirtsinbulk []
4.5 fa-shopping-bag []
4.5 fa-shopping-basket []
fa-shopping-cart []
fa-sign-in []
4.6 fa-sign-language []
fa-sign-out []
fa-signal []
4.6 fa-signing (alias) []
4.3 fa-simplybuilt []
fa-sitemap []
4.3 fa-skyatlas []
fa-skype []
4.1 fa-slack []
4.1 fa-sliders []
4.2 fa-slideshare []
fa-smile-o []
4.6 fa-snapchat []
4.6 fa-snapchat-ghost []
4.6 fa-snapchat-square []
4.2 fa-soccer-ball-o (alias) []
fa-sort []
fa-sort-alpha-asc []
fa-sort-alpha-desc []
fa-sort-amount-asc []
fa-sort-amount-desc []
fa-sort-asc []
fa-sort-desc []
fa-sort-down (alias) []
fa-sort-numeric-asc []
fa-sort-numeric-desc []
fa-sort-up (alias) []
4.1 fa-soundcloud []
4.1 fa-space-shuttle []
fa-spinner []
4.1 fa-spoon []
4.1 fa-spotify []
fa-square []
fa-square-o []
4.0 fa-stack-exchange []
fa-stack-overflow []
fa-star []
fa-star-half []
fa-star-half-empty (alias) []
fa-star-half-full (alias) []
fa-star-half-o []
fa-star-o []
4.1 fa-steam []
4.1 fa-steam-square []
fa-step-backward []
fa-step-forward []
fa-stethoscope []
4.4 fa-sticky-note []
4.4 fa-sticky-note-o []
fa-stop []
4.5 fa-stop-circle []
4.5 fa-stop-circle-o []
4.3 fa-street-view []
fa-strikethrough []
4.1 fa-stumbleupon []
4.1 fa-stumbleupon-circle []
fa-subscript []
4.3 fa-subway []
fa-suitcase []
fa-sun-o []
fa-superscript []
4.1 fa-support (alias) []
fa-table []
fa-tablet []
fa-tachometer []
fa-tag []
fa-tags []
fa-tasks []
4.1 fa-taxi []
4.4 fa-television []
4.1 fa-tencent-weibo []
fa-terminal []
fa-text-height []
fa-text-width []
fa-th []
fa-th-large []
fa-th-list []
4.6 fa-themeisle []
fa-thumb-tack []
fa-thumbs-down []
fa-thumbs-o-down []
fa-thumbs-o-up []
fa-thumbs-up []
fa-ticket []
fa-times []
fa-times-circle []
fa-times-circle-o []
fa-tint []
fa-toggle-down (alias) []
4.0 fa-toggle-left (alias) []
4.2 fa-toggle-off []
4.2 fa-toggle-on []
fa-toggle-right (alias) []
fa-toggle-up (alias) []
4.4 fa-trademark []
4.3 fa-train []
4.3 fa-transgender []
4.3 fa-transgender-alt []
4.2 fa-trash []
fa-trash-o []
4.1 fa-tree []
fa-trello []
4.4 fa-tripadvisor []
fa-trophy []
fa-truck []
4.0 fa-try []
4.2 fa-tty []
fa-tumblr []
fa-tumblr-square []
4.0 fa-turkish-lira (alias) []
4.4 fa-tv (alias) []
4.2 fa-twitch []
fa-twitter []
fa-twitter-square []
fa-umbrella []
fa-underline []
fa-undo []
4.6 fa-universal-access []
4.1 fa-university []
fa-unlink (alias) []
fa-unlock []
fa-unlock-alt []
fa-unsorted (alias) []
fa-upload []
4.5 fa-usb []
fa-usd []
fa-user []
fa-user-md []
4.3 fa-user-plus []
4.3 fa-user-secret []
4.3 fa-user-times []
fa-users []
4.3 fa-venus []
4.3 fa-venus-double []
4.3 fa-venus-mars []
4.3 fa-viacoin []
4.6 fa-viadeo []
4.6 fa-viadeo-square []
fa-video-camera []
4.4 fa-vimeo []
4.0 fa-vimeo-square []
4.1 fa-vine []
fa-vk []
4.6 fa-volume-control-phone []
fa-volume-down []
fa-volume-off []
fa-volume-up []
fa-warning (alias) []
4.1 fa-wechat (alias) []
fa-weibo []
4.1 fa-weixin []
4.3 fa-whatsapp []
4.0 fa-wheelchair []
4.6 fa-wheelchair-alt []
4.2 fa-wifi []
4.4 fa-wikipedia-w []
fa-windows []
fa-won (alias) []
4.1 fa-wordpress []
4.6 fa-wpbeginner []
4.6 fa-wpforms []
fa-wrench []
fa-xing []
fa-xing-square []
4.4 fa-y-combinator []
4.1 fa-y-combinator-square (alias) []
4.1 fa-yahoo []
4.4 fa-yc (alias) []
4.1 fa-yc-square (alias) []
4.2 fa-yelp []
fa-yen (alias) []
4.6 fa-yoast []
fa-youtube []
fa-youtube-play []
fa-youtube-square []
';
$subst = "\2\t\3\t\1\n";
$result = preg_replace($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