PHP string has a length, but the content is empty?

PHP, look at the graph, string length is 413, but the content is empty '? What's the reason?

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PHP, look at the graph, string length is 413, but the content is empty '? What's the reason?

 
  ';}? >

See what the ASC code corresponds to and know what's inside.

It really doesn't matter. or those invisible characters. Empty a grid only when it is displayed
\t\n\r will have this effect, but it will show a space in double quotes ""
And \f\1\2\3\4\5\6\7\0, are not even a space, that is, ""
double quotes, harm.

What this string is, if it can't be pasted, it's either an empty string, \ r \ n \ t is possible

!--? php$a = "\t\t\t\t\t\t"; var_dump ($a); Strint (6) ""  
 
 
 Most of it has " "
 
 
 
 
 HTML display will merge contiguous spaces of 1 
 
 You can use the Browser to see the source code mode, 
 
 Chrome is in front of the address bar to add View-source on the line ah 
 
view-source:http:// ......
 
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