Clear HTML string from white spaces and new line character. It returns clean html string to be used inside JSON, AJAX etc.

gistfile1.txt

//Eu tenho a seguinte string que representa um código html gerado dinamicamente por php.
//Preciso filtrar novas linhas e espaços em brancos para ser formatado corretamente num string JSON para
//Ser enviado através de AJAX.

<ul class="list-group sidebar-nav-v1 margin-bottom-40" id="menuHomeUserPrivate">    
<li class="list-group-item active">
    <a id="to_ProfileOverall" class="privateMenuLinkJS"><i class="fa fa-bar-chart-o"></i> Overall</a>
</li>
<li class="list-group-item list-toggle">
    <a data-toggle="collapse" data-parent="#menuHomeUserPrivate" href="#collapse-MoneyManage" ><i class="fa fa-money"></i> Invoice</a>
    <ul id="collapse-MoneyManage" class="collapse">
        <li><a id="to_MoneyManagerFaturamentoInsert" class="privateMenuLinkJS"><i class="fa  fa-level-down"></i> Big Invoice  </a></li>
        <li><a id="to_MoneyManagerFaturamentoGerir" class="privateMenuLinkJS"><i class="fa  fa-cogs"></i> Big big big

 Invoice 2  </a></li>
    </ul>
 </li>
</ul>



//O objetivo é transformar em uma string de uma só linha, filtrar espaços em branco e new lines.

<ul class="list-group sidebar-nav-v1 margin-bottom-40" id="menuHomeUserPrivate"><li class="list-group-item active"><a id="to_ProfileOverall" class="privateMenuLinkJS"><i class="fa fa-bar-chart-o"></i>Overall</a></li><li class="list-group-item list-toggle"><a data-toggle="collapse" data-parent="#menuHomeUserPrivate" href="#collapse-MoneyManage" ><i class="fa fa-money"></i> Invoice</a><ul id="collapse-MoneyManage" class="collapse"><li><a id="to_MoneyManagerFaturamentoInsert" class="privateMenuLinkJS"><i class="fa  fa-level-down"></i>Big Invoice</a></li><li><a id="to_MoneyManagerFaturamentoGerir" class="privateMenuLinkJS"><i class="fa  fa-cogs"></i>Big big big Invoice 2</a></li></ul></li></ul>

//Então essa é a abordagem:
//Gerar o html dinamicamente com o heredoc http://php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc

$htlmString=<<<EOF

<ul class="list-group sidebar-nav-v1 margin-bottom-40" id="menuHomeUserPrivate">    
<li class="list-group-item active">
    <a id="to_ProfileOverall" class="privateMenuLinkJS"><i class="fa fa-bar-chart-o"></i> Overall</a>
</li>
<li class="list-group-item list-toggle">
    <a data-toggle="collapse" data-parent="#menuHomeUserPrivate" href="#collapse-MoneyManage" ><i class="fa fa-money"></i> Invoice</a>
    <ul id="collapse-MoneyManage" class="collapse">
        <li><a id="to_MoneyManagerFaturamentoInsert" class="privateMenuLinkJS"><i class="fa  fa-level-down"></i> Big Invoice  </a></li>
        <li><a id="to_MoneyManagerFaturamentoGerir" class="privateMenuLinkJS"><i class="fa  fa-cogs"></i> Big big big

 Invoice 2  </a></li>
    </ul>
 </li>
</ul>

EOF;

$re = "/(?:\\s*([<>])\\s*|(\\s)\\s*)/im"; 
$subst = "$1$2"; 

$htmlDone = preg_replace($re, $subst, $str);


Fonte:http://stackoverflow.com/questions/35732977/regex-how-to-remove-white-spaces-and-new-lines-in-html-code