In a PHP code, appearance of namespace is resolved subject to following rules −
A namespace identifier without namespace separator symbol (/) means it is referring to current namespace. This is an unqualified name.
If it contains separator symbol as in myspace\space1, it resolves to a subnamespace space1 under myspace. Such type of naming is relative namespace.
Name of fully qualified namespace starts with \ character. For example, \myspace or \myspace\space1.
Fully qualified names resolve to absolute namespace. For example \myspace\space1 resolves to myspace\space1 namespace
If the name occurs in the global namespace, the namespace\ prefix is removed. For example namespace\space1 resolves to space1.
However, if it occurs inside another namespace, it is treated differently. For example, if namespace\space1 is inside myspace, it is equivalent to myspace\space1
First segment of the name in qualified name is translated according to the current class/namespace import table.
If no import rule applies, the current namespace is prepended to the name.
class-like names are translated according to the class/namespace import table, function names according to the function import table and constants according to the constant import table.
For unqualified names, if no import rule applies and the name refers to a function or constant and the code is outside the global namespace, the name is resolved at runtime. First it looks for a function from the current namespace, then it tries to find and call the global function.