unnecessary quotes around json values

[hosemaria]

I have to send JSON data from PHP server to Javascript. JSON data
after json_encode() looks like this:

{"colNames":["Measure ID","Name"],
"url":"measure_JSON.php?nd='+new Date().getTime()",
"editurl":"measure_add.php",
"datatype":"json",
"sortname":"name",
"imgpath":"..\/js\/jqgrid\/themes\/steel\/images",
"viewrecords":true,
"cellEdit":true,
"sortorder":"asc",
"height":"100%",
"toolbar":[true,"top"],
"cellsubmit":"clientArray",
"multiselect":true,
"loadui":"block",
"pager":"#pager2,#pager",
"rowNum":100,"rowList":[10,20,30,50,100],
"caption":"Measure",
"colModel":
[{"name":"id_item","index":"id_measure","editable":true,"width":30},
{"name":"name","index":"name","editable":true,"width":130}]}

1. Second line
"url":"'measure_JSON.php?nd='+new Date().getTime()",
How to get rid of quotes(") around "'measure_JSON.php?nd='+new Date
().getTime()"?
json_encode add (") quotes automaticaly and i can't find option to
switch it off.
Javascript need to run operation new Date().getTime(). With quotes it
is treated as string so no execution is performed.