Why should var_dump be used for PHP connection output?

Why should var_dump be used for PHP link output? Why should I use the & nbsp; var_dump variable for output during PHP connection ?, Because var_dump can view all php Data Class PHP links, why should var_dump be used for output?
Why should var_dump be used for PHP link output?
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Because var_dump can view all php Data types:
Scalar, resource, array, and object.

Mysql_query returns a resource type, which cannot be viewed using echo, print, and print_r.
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Echo, print_r, and var_dump:

Echo outputs the string and value. it is not a function and has no return value.
Print_r prints a composite type, such as an array object.
Var_dump displays the structure information about one or more expressions, including the expression type and value. The array recursively expands the value and displays its structure through indentation.

I was confused at the beginning and now I understand it.