PHP variable assignment, substitution into variables in JavaScript, assignment javascript_PHP tutorial

Assign values ​​to PHP variables and substitute them into variables in JavaScript, assign values ​​to javascript

Copy code The code is as follows:
$(document).ready(function(){

var t=;
alert(t)
})

or
Copy code The code is as follows:
$(document).ready(function(){

var t="";
alert(t)
})

or
Copy code The code is as follows:

The key is that sd must be surrounded by single quotes and quotation marks, otherwise it will be displayed
“sd is not defined
[Break at this error] 
var t=sd;”
sd is a variable without quotes. If the variable has not been defined before, if it is assigned to another variable, of course an error will be reported