jQuery + LaTeX + PHP

<script type='text/javascript' src='js/jquery.js'></script>

<script type='text/javascript' src='js/jquery.jslatex.js'></script>

/* LaTeX */

$(function () {  
	
	$(".latex").latex();  
		
});
	
/* Instant preview */

$(document).ready(function() {
	
	$('#live-preview-form input, #live-preview-form textarea').bind('blur keyup',function() {
	  
		$('#lp-comment').text($('#comment').val());
		
		$('#lp-comment').html($('#lp-comment').html()
		.replace(/\n/g,'<br />'));

		$('#lp-comment').html($('#lp-comment').html()
		.replace(/\[math\]/g   , '<div class=\'latex\'>').replace(/\[(\/)math\]/g  , '</div>'));
		
	});
	  
});

<!-- Textarea -->

<div id="live-preview-form" class="lp-block">

	<textarea name="comment" id="comment"></textarea>

</div>

<!-- Instant preview block -->

<div id="live-preview-display" class="lp-block">

	<div id="lp-comment"></div>

</div>

Решите пример: [math]\int_{0}^{\pi}\frac{x^{4}\left(1-x\right)^{4}}{1+x^{2}}dx =\frac{22}{7}-\pi[/math]!