请问一段PHP代码是什么意思？

<?phpif ($_REQUEST['root'] == "source"):?>[	{		"text": "1. Pre Lunch (120 min)",		"expanded": true,		"classes": "important",		"children":		[			{				"text": "1.1 The State of the Powerdome (30 min)"			},		 	{				"text": "1.2 The Future of jQuery (30 min)"			},		 	{				"text": "1.2 jQuery UI - A step to richnessy (60 min)"			}		]	},	{		"text": "2. Lunch  (60 min)"	},	{		"text": "3. After Lunch  (120+ min)",		"children":		[			{				"text": "3.1 jQuery Calendar Success Story (20 min)"			},		 	{				"text": "3.2 jQuery and Ruby Web Frameworks (20 min)"			},		 	{				"text": "3.3 Hey, I Can Do That! (20 min)"			},		 	{				"text": "3.4 Taconite and Form (20 min)"			},		 	{				"text": "3.5 Server-side JavaScript with jQuery and AOLserver (20 min)"			},		 	{				"text": "3.6 The Onion: How to add features without adding features (20 min)",				"id": "36",				"hasChildren": true			},		 	{				"text": "3.7 Visualizations with JavaScript and Canvas (20 min)"			},		 	{				"text": "3.8 ActiveDOM (20 min)"			},		 	{				"text": "3.8 Growing jQuery (20 min)"			}		]	}]<?php else: sleep(1); ?>[	{		"text": "1. Review of existing structures",		"expanded": true,		"children":		[			{				"text": "1.1 jQuery core"			},		 	{				"text": "1.2 metaplugins"			}		]	},	{		"text": "2. Wrapper plugins"	},	{		"text": "3. Summary"	},	{		"text": "4. Questions and answers"	}	]<?php endif; ?>